Ancient name of Mosby was Morseby.

When William Rufus and later Henry I of England were establishing the border between England and Scotland, one great reliance was the aid of the Cumberland Barons. Among these the names of de Lucy, de Tylliol and de Moresby constantly appear. In nearly every border Barony of the District, the de Morsebys came to have a share by gift, inheritance or marriage with sons and daughters of powerful houses, and alliances between the de Tylliols, de Lucys and de Morsebys occur in early and late generations.

The Pariah of Morseby, which in 1801 contained 2165 acres of land border-ing on the coast of Cumberland County, along side lay Distington, in which also the de Morsebys had interest.

Hutchinson says that the situation of Morseby on the South Banks of a bay for shipping on the mouth of the Little River, shows clearly the intention of the Romans to form a chain of stations or castle forts on the coast of the Irish Sea.

The surname of Mosby is a form of the old de Morseby which in turn sprang from Mauriceby, Moriceby or Morrysby, meaning Mona or Maurice's dwelling or bye. Wales is named as the probably birth-place of the original Mona or Maurice who gave his name to the Manor of Morseby.

The immediate line of the early house of Morseby as far as found, places on Urhman after Moris. The former was followed by Hugonis, and redorded him-self formally witnessing a Charter in 1192. A Thomas, Lord of To' raeby, is named as in the reign of King John. Sir Hugh de Morseby and 1240 Hugonis de Morseby add their names to the line. In 1250 Nicholas was recorded, while in 1270 was one Rodan de Morseby, followed in 1326 by that of Thomas de Morseby, who married Margaret, a daughter of Thomas de Lucy, Lord of Coekermouth, an important adjunct to Carleel, now Carlisle, from whom the Mosbys in America are descended.

About this time Sir Hugh de Morseby was of the Knights called to the aid of Carleel (Carlisle) for which services he received Calgaith near Penrith, In 1329 Sir Hugh was listed as a Knight of the Shire. Later a Morseby held the same post for Cumberland, His son, Christopher succeeded him in family estates and offices. He was followed in 1414 by another Hugh.

The de Morsebys left memorials in Penrith as well as in other places in England. A county saying which shows the popular esteem in which the family was held was "as good as Morseby, his folk."

A new old light has recently fallen on the pages of Morseby history. In 19ll there was found in the attic of an ancient mansion in England, some heraldic manuscripts of rare value, among them a parchment-bound book in sirteenth century writing recording herladic visitations of the north of England made between 1552 and 1657. A part of these records concerns the Morsebys and links the name with that of Fairfax, through the marriage of Thomas Fayrefaxe, (Fairfax) with the daughter of a Morseby.
A daughter of Iven Etton is recorded as the wife of Sir Christopher Morseby. this record being in the pedigree of ~Sir Nicholas Fayrefax of Gyllings in Yorkshire, Knight." In later years Sir Fairfax Morseby, Knight of Litchfield, appears in English records. His descendants had a part in making English history.

In the 15th century the marriage of Margaret Tylliol to James Morseby is recorded. She was descended from Richard the Rider, surnamed Tylijolti, who received from Henry 1, the lordship or Carlisle. Margaret after the death of her husband, married Nicholas Musgrave. it was one of her heirs, Sir Edward Musgrave, who bought the Morseby share of the maternal estate and built Scaleby Castle. 15th and 16th century records show that the Morsebys were of the class entitled to "bear arms". A marble slab in the south wall of the chancel of the parish church in Fenrith is charged with the arms of Morseby "across in the first quarter of cingue foil". The slab is a memorial to Christopher Morseby and is dated 1459.

The register in the church of Carshalten in Croyden begins in 1538 and contains Morseby records. There is also a mutilated brass plate bearing an inscription concerning the daughter of Raynoldi Morseby of the county of Casterbury.

That the descendants of the ancient de Morseby who became Mosbys, retained the family standing is shown by the fact that those who emigrated to America were classed as "gentlemen" and were from the first possessed of lands and means.

The Mosby family in America is typically Virginian and has been closely associated with that State from the time of its early settlement.

The original emigrant seems to have been Edward Mosby, who, in about 1650 was a member of Westover parish in Charles City, a colony of Virginia near Richmond.