Here are explanations behind some of the more obscure mech names; others are left off as self-explanatory.
Inner Sphere Mechs
NAME : Name Info
Akuma : Japanese devil or demon
Albatross : a bird of bad luck; a curse
Avatar : earthly incarnation of a Hindu god
Bandersnatch : Beast from "Jabberwocky"
Banshee : Irish tradition of women wailing for the dead; associated with a deadly ghost
Barghest : Legendary creature- devil-dog
Beowulf : mytho-historical hunter-hero who fought Grendel
Bishamon : Japanese warrior monk
Blackjack : a lead-filled sack used as a club
Blitzkrieg : "lightning war" - Nazi fighting style
Cataphract : Byzantine heavy cavalry
Cerberus : Greek hound guarding the Underworld gates
Cestus : armored battle-gauntlet for gladitorial fights
Cicada : Why is this named for a shell-shedding bug?
Clint : for Clint Eastwood
Copperhead : Small poisonous snake
Cossack : Hardy horseback tribesmen of the Russian steppes
Crockett : for Davy Crockett
Cudgel : a war club
Daedlus : Greek mythical inventor
Daikyu : powerful Japanese bow
Daimyo : title of a Japanese warlord
Dervish : desert Sufi tribesmen; known for "whirling" in mystical trance
Duan Gong : short bow
Enfield : British WW2 rifle
Epimetheus : brother of Greek Titan Prometheus
Gallowglas : Irish mercenaries
Garm : Norse wolf guarding the underworld gates
Hatamoto-Chi : Japanese ceremonial rank (-Earth)
Hatamoto-Hi : Japanese ceremonial rank (-Fire)
Hatamoto-Kaze : Japanese ceremonial rank (-Wind)
Hatamoto-Ku : Japanese ceremonial rank (-Void)
Hatamoto-Mizo : Japanese ceremonial rank (-Water)
Hauptmann : German Captian
Helios : Greek god who drove the Sun across the sky in his chariot
Highlander : Scottish clan warriors
Hollander : Dutch mercenaries
Hoplite : Greek footsoldier
JagerMech : "hunter-mech"
Jenner : Bruce Jenner, Olympic medalist runner
Jing Gao : "alert" or "warn"
Kabuto : Japanese battle-helmet
Kintaro : "ape"; a super-strong Japanese hero
Komodo : largest living land dragon
Koto : Japanese harp
Mackie : for Fleet Admiral MacKenna, founder of Terran Hegemony
Men Shen : God who guards doorways
Morpheus : a god of sleep and dreams
Naginata : Japanese bladed polearm
Nexus : point of coming together; a pinnacle
No-Dachi : Long japanerse sword
O-Bakemono : "Great Goblin"
Owens : "Garry Owen", a frontier song, not "Gray Owens"
Raijin : Wind
Rakshasa : mythical creature that assumed its victims' forms
Ronin : masterless Samurai
Salamander : a mythical fire-dwelling creature
Sasquatch : yeti; "bigfoot"
Scarabus : related to the scarab, a beetle sacred in egyptian mythology
Shogun : Japanese warlord of great power
Shugenja : Magic-user
Sirocco : a hot mediterranean wind
Sunder : to tear apart
Tai-Sho : Kurita General rank
Ti Ts'Ang : The King of the Earth's Womb; above Yen Lo Wang
Toyama : for Blake hero Conrad Toyama
Trebuchet : very large catapult-like device
Vindicator : one who justifies or proves correct
Whitworth : British gun genius
Wyvern : small proto-dragon
Yen-Lo-Wang : Chinese god of the dead
Yeoman : Welsh longbowman or naval petty officer
Yu Huang : Jade Emperor; head of Chinese pantheon
Clan Mechs
NAME : Name Info
Bane : an enemy or evil
Behemoth : biblical dragon
Black Lanner : Bird of prey
Blood Kite : a bird of prey
Canis : latin genus name for wolf / dog
Corvis : latin genus name for raven
Daishi : "great death"
Dire Wolf : giant prehistoric wolf
Fenris : giant wolf of Norse myth
Great Wyrm : large, old dragon
Grendel : creature slain by mythic hero beowulf
Ha Otoko : "blade-wielder"; soldier
Hankyu : japanese shortbow
Incubus : male succubus, a seductive demon
Kingfisher : fish-eating bird
Kodiak : huge bear
Koshi : "little death"
Kraken : gigantic squid creature of old sefaring legend
Loki : Norse trickster god
Man O'War : Stinging jellyfish or heavily armed ship
Mandrill : vicious carnivorous ape
Masakari : Battle axe
Naga : poisonous snake
Night Gyr : related to gyrfalcon, a predatory bird
Nobori-nin : "banner-bearer"
Peregrine : a small falcon
Ryoken : hunting dog
Thresher : a type of shark
Turkina : Name of a Jade Falcon Khan's pet
Uller : Norse god of archery
Ursus : latin genus name for bear
Vixen : a female fox