Names begining with "Le" are listed under the first letter
following the prefix
e.g. Le Boutillier under "B".
| Family Name | Gaelic Equivalent | Original language | English Translation |
| Lacey | De L�is | Meritus augentur honores. | Honours are enhanced by deserts. |
| Lambe | � Luam | Per mare per terras. | By sea and land. |
| Lambert | Laimbeart | Ut quocunque paratus. | That I may be prepared on every side. |
| Lamont | Mac Lagmainn | Ne parcas nec spernas. | Neither spare nor scorn. |
| Lane | Mac Giollae�in | Celeriter. | Swiftly. |
| Langan | � Laigin | Confide recte agens. | Trust in fair dealing. |
| Larkin | � Lorc�in | Chirsto duce vincamus. | With Christ I will conquer. |
| Lavin | � Maoil�imin | Fortuna audaces juvat. | Fortune favours the bold. |
| Law | De L� | Non obscura nec ima. | Neither obscure nor very low. |
| Lawless | Laigl�is | Virtute et numine. | By virtue and prudence. |
| Lawlor | � Leatlobair | Fortis et fidelis. | Brave and faithful. |
| Lawrence | - | Quoe pense. | What do you think. |
| Lawson | Mac Labrain | Leve et reluis. | Arise and re-illumine. |
| Leydon | � Loide�in | Forti non ignavo. | To the brave man, not to the dastard. |
| Leahy | � Laoca | Tout vient de Dieu. | All comes from God. |
| O'Leary | � Laoire | L�idir � rig an lir. | Strong is the king of the sea. |
| Lee | � Laoi | Courageux. | Courageous. |
| Leech | Lia | Virtute et valore. | With virtue and valour. |
| Lenihan | � Loingeac�in | Patriae inflici fidelis. | Faithful to my unhappy country. |
| Lennon | (�) Mac Leann�in | Prisco stripe Hibernico. | Of ancient Irish stock. |
| Len(n)ox | Mac Caiseal�in | En la rose je fleurie. | I flourish in the rose. |
| Leonard | � Loin�n | Pour bien desirer. | For wishing well. |
| Lewis | Lobaois | Bidd llu hebb llydd. | In the path of an army, no man can stand. |
| Lindsay | � Loinsig | Endure fort. | Suffer bravely. |
| Little | � Beac�in | Magnum in parvo. | Much in little. |
| Lloyd | L�id | Heb Dduw heb ddin a Duw a digon. | Without God, without anything, God is enough. |
| Loftus | � Lactnain | Loyal � mort. | Loyal to death. |
| Logan | � Leoc�in | Hoc majorum virtus. | This is the valour of my ancestors. |
| Lonergan | � Longarg�in | L�m l�idir in uactar. | The strong hand uppermost. |
| Long | � Long�in | Confide recte agens. | Doing rightly be confident. |
| Looney | � Luanaig | - | I am not alone. |
| Mc Loughlin | Mac Loclainn | Cuimnig ar do geallamnaca. | Remember your promies. |
| O'Loughlin | � Loclainn | Anchora salutis. | The anchor of salvation. |
| Loughnan | � Lactn�in | Fortis et fidus. | Brave and faithful. |
| Lowe | Mac L� | Spero meliora. | I hope for better things. |
| Lowry | Mac Labr�i | Virtus semper viridis. | Virtue is always flourishing. |
| Lucas | Mac L�c�is | Respice finem. | Regard the end. |
| Lucey | � Luasaig | Be trwgh and delygent. | By truth and diligence. |
| Lydon | � Laoid�ain | Forti non ignavo. | To the brave man, not to the dastard. |
| Lynam | � Laigean�in | Fortis et constans. | Bold and constant. |
| Lynch | � Loinsig | Semper fidelis. | Always faithful. |
| Lyons | � Laigin | Noli irritare leonem. | Do not irritate the lions. |
| Mc Lysaght | Mac Giolla Lascta | Congnam � Dia. | Help from God. |
| Mac Lachlan | - | Fortis et fidus. | Brave and trusty. |
| M' Lachlan | - | Fortiter. | Boldly |
| Laffan | - | Vincit omnia virtus. | Virtue conquers all. |
| Laforey | - | Loyal aut mort. | Loyal to the death. |
| Laird | - | Spero meliora. | I hope for better things. |
| Lalor | - | Fortis et fidelis. | Brave and faithful. |
| Lamb | - | Levius fit patientia. | Patience makes burdens lighter. |
| Lamb | - | Virtute et fide. | By valour and faith. |
| Lambard | - | Deo patria tibi. | For God, country, and yourself. |
| Lane | - | Garde la Roy | Guard the King. |
| Langholme | - | In cruce salus. | Salvation from the cross. |
| Langlands | - | Spero. | I hope. |
| Langley | - | - | Beare and forbeare. |
| Langley | - | Fide sed cui vide. | Trust, but be careful whom (you trust). |
| Langton | - | Loyal aut mort. | Loyal to the death. |
| Langton | - | Sursum corda. | Hearts upwards. |
| M' Lannahan | - | - | Virtue is my honour. |
| Lanphier | - | Virtute et fidelitate. | By valour and fidelity. |
| Laslett | - | Finem respice. | Consider the end. |
| Lauder | - | Virtute. | By virtue. |
| Mc Laughlin | - | Fortis et fidus. | Brave and trusty. |
| Laurie | - | Virtus semper viridis. | Virtue is always flourishing. |
| Law | - | - | Trusty and kind. |
| Lawford | - | In Deo confido. | I trust in God. |
| Lawford | - | In utrumque paratus. | Prepared for both. |
| Lawrence | - | - | Be ready. |
| Lawrence | - | In cruce salus. | Salvation from the cross. |
| Lawrie | - | - | I'll be wary. |
| Lawson | - | - | Loyal, secret; Loyal, confidential. |
| Lawson | - | - | Rise and shine. |
| Lawson | - | Dominus providebit. | God will provide. |
| Lay | - | - | Through. |
| Leake | - | Perseverando. | By perservering. |
| Learmonth | - | Dum spiro spero. | While I breath I hope. |
| Learmonth | - | Spero. | I hope. |
| Leater | - | Favente Deo. | By Gods favour. |
| Leck | - | Virtutis praemium. | Virtues reward. |
| Lecky | - | Semper paratus. | Always prepared. |
| Lee | - | Deus fortitudo mea. | God is my strength. |
| Lee | - | Dum spiro spero. | While I breath I hope. |
| Lee | - | Fide et fortitude. | By fidelity and fortitude. |
| Lefevre | - | Sans changer. | Without changing. |
| Legg | - | Gaudet tenamine virtus. | Virtue exults in the trial. |
| Leicester | - | Pro rege et patria. | For king and country. |
| Leigh | - | Tout vient de Dieu. | All comes from God. |
| Leighton | - | - | Dread shame. |
| Leith | - | - | Trusty to the end. |
| Lennard | - | Patriae inflici fidelis. | Faithful to my unhappy country. |
| Lennard | - | Pour bien desirer. | For wishing well. |
| Lennox | - | - | I'll defend. |
| Mac Leod | - | - | Hold fast. |
| Mac Leod | - | - | I ruke while I see. |
| Leslie | - | - | God guide all. |
| Leslie | - | - | Grip fast. |
| Leslie | - | - | Hold fast. |
| Leslie | - | - | Keep fast. |
| Leslie | - | Pro rege et patria. | For king and country. |
| Leslie | - | Soli Deo gloria. | Glory to God alone. |
| Lethbridge | - | Spec mea in Deo. | God is my hope. |
| Levin | - | Certavi et vici. | I have fought and conquered. |
| Lewin | - | Spec mea in Deo. | God is my hope. |
| Lewis | - | - | Be wise as a serpent, harmless as a dove. |
| Lewis | - | A deo et rege. For God and king. For God and king. | - |
| Lewis | - | Patriae fidus. | Faithful to my country. |
| Leyland | - | - | God feedeth ye land. |
| Lidderdale | - | - | Foresight is all. |
| Lievre | - | Gardez bien. | Guard well. |
| Lighton | - | Fortitudine et prudentia. | With fortitude and prudence. |
| Lindow | - | Vi et virtute. | By strength and valour. |
| Lindsay | - | Toujours loyal. | Always loyal. |
| Lister | - | Malo mori quam foedari. | Death rather than dishonour. |
| M' Liver | - | - | Be mindful. |
| Liverpool | - | Deus nobis haec otia fecit. | God has given us this tranquility. |
| Llewellyn | - | Vincit qui patitur. | The one who is patient wins. |
| Lloyd | - | Fide et fortitude. | By fidelity and fortitude. |
| Lloyd | - | Frangas non flectes. | You may break, but shall not bend me. |
| Lloyd | - | Iddow Bor dioleh. | To God be thanks. |
| Lloyd | - | Sic itir ad astra. | This is the way of the stars. |
| Lloyd | - | Spectemur agendo. | Let us be judged by our actions. |
| Locock | - | Victoria. | Victory. |
| Loft | - | Fide et fortitude. | By fidelity and fortitude. |
| Loftie | - | Loyal aut mort. | Loyal to the death. |
| Loftus | - | Loyal aut mort. | Loyal to the death. |
| Login | - | - | By the grace of God. |
| Lone | - | - | Lone. |
| Longley | - | Esse quam videri. | To be, rather than to seem. |
| Lorimer | - | - | Onward. |
| Lorimer | - | - | Upward. |
| Mc Loskey | - | Sica inimicis. | A dagger to his enemies. |
| Lowndes | - | - | Ways and means. |
| Lucy | - | - | With truth and diligence. |
| Ludlow | - | Nec temere nec timide. | Neither rashly nor timidly. |
| Lukis | - | Esse quam videri. | To be, rather than to seem. |
| Lumb | - | Respice finem. | Regard the end. |
| Lumsden | - | - | Beware in time. |
| Lund | - | Semper fidelis. | Always faithful. |
| Luscombe | - | Deo duce fero commitante. | God my guide, my strength, and companion. |
| Lutwidge | - | Deo patria amicas. | To God, country, and friends. |
| Lyde | - | Non sibi. | Not for himself. |
| Lyell | - | Forti non ignavo. | To the brave man, not to the dastard. |
| Lynch | - | Cor mundum crea in me Deus. | Create in me a clean heart O God. |
| Lynch | - | Nec temere nec timide. | Neither rashly nor timidly. |
| Lyon | - | Pro rege et patria. | For king and country. |
| Lyons | - | Virtute et fidelitate. | By valour and fidelity. |
| Lyster | - | Loyal aut mort. | Loyal to the death. |
| Lyttel | - | Magnum in parvo. | Much in little. |
| Sources: | |
| Irish Family Mottoes | "The General Armory of England, Scotland, Ireland, and Wales." |
| By Tom�s � Baoill | by Sir John Bernard Burke |