"companion in arms, follower of a knight, outlaw, etc.," is attested from late 14c., from merry (adj.) + man (n.). Related: Merry men.
As long fives the merry-man, as the wretch for all the craft he can.
The Merry-man and his maid, however, tell us that they can sing and dance too, a wonderful accomplishment.
Henry A. Lytton