Yours, Etc.: Origins and Uses of 8 Sign-Offs
c.1300, from Old French compagnon "fellow, mate, friend, partner" (12c.), from Late Latin companionem (nominative companio), literally "bread fellow, messmate," from Latin com- "with" (see com-) + panis "bread" (see food).
Found first in 6c. Frankish Lex Salica, and probably a translation of a Germanic word (cf. Gothic gahlaiba "messmate," from hlaib "loaf of bread"). Replaced Old English gefera "traveling companion," from faran "go, fare."