The exact origin of the Hosmer/Osmer name is lost in history. It is, however, an extremely old name. There are two schools of thought regarding the name's first appearance on the Continent. Accourding to one source, the name originated in Northern Germany around the year 547 A.D., in the political division, the Duchy of Sleswick. This land was the home of the Angles. In 547 A.D,. the Anglian chiedtain Ida led his countrymen in an invasion of England. These fierce Teutonic warriors crossed the North Sea in forty small vessels and landed in a region between the Tweed and the Frith of Forth (the east coast of Northern England and Southern Scotland). Accompanying Ida on this historic enterprise, were his twelve sons. One of these sons was named Osmer. It is interesting to note that Ida, later appointed king by his fellow chieftains, claimed an ancestral link to the legendary Anglo-Saxton chieftain, Woden (3rd century A.D.).
A second source advanced the theory that the name originated in Bavaria. According to this authority, the name appeared in Bavaria as, Ujsmer. It is said that those who bore the patronym were members of a now extinct branch of Bavarian nobility. Before the name died out in Bavaria, some individuals of the Usmer clan emigrated to England, where the Bavarian family name evolved to the English surname, Hosmer. Identity of the individuals, the location of their first settlement and the exact date of this emigration are lost in the mists of time.
Both theories point to a Germanic origin. Tis is possible that both theories are correct and that they point to a dual penetration of the name into England, separated by both time and location.
Official records of the period clearly show that the Osmaer name (along with its various equvalents) existed in Devonshire and Dorsetshire, England as early as the 11th century. According to one source, America's Hosmers are directly descended from "an ancient Dorsetshire family". There is no documentation for this assertion, but it sound quire plausible, given the historical occurrences of the name. Genealogically speaking, our knowledge of the Hosmer family goes back only as far as the middle 1500s. These early Hosmer ancestors lived in Eastern Sussex, England. How long the family had lived in Sussex is unknown, but it could have been for a considerable period of time.