The definition of a fellow is a man or a boy, especially a boyfriend or lover. The definition of a fellow is also a peer who is doing the same activities as you, or a student or scholar doing research that is being paid for.
(noun)See fellow in Webster's New World College Dictionary
noun
Origin: ME felaghe < Late OE feolaga, partner < feoh (see fee) + laga, a laying down (see law), after ON félagi: basic sense, “one laying down wealth for a joint undertaking”; fellowsenses , , , after L socius: see associate
adjective
See fellow in American Heritage Dictionary 4
noun
Origin:
Origin: Middle English felau
Origin: , from Old English fēolaga
Origin: , from Old Norse fēlagi, business partner, fellow
Origin: , from fēlag, partnership
Origin: : fē, property, money; see peku- in Indo-European roots
Origin: + lag, a laying down; see legh- in Indo-European roots
. Word History: A jolly good fellow might or might not be the ideal business associate, but the ancestor of our word fellow definitely referred to a business partner. Fellow was borrowed into English from Old Norse fēlagi, meaning “a partner or shareholder of any kind.” Old Norse fēlagi is derived from fēlag, “partnership,” a compound made up of fē, “livestock, property, money,” and lag, “a laying in order” and “fellowship.” The notion of putting one's property together lies behind the senses of fēlagi meaning “partner” and “consort.” In Old Icelandic fēlagi also had the general sense “fellow, mate, comrade,” which fellow has as well, indicating perhaps that most partnerships turned out all right for speakers of Old Icelandic.Learn more about fellow