companion:  Etymologically, your companion is someone who shares your ‘bread’ with you. It comes, via Old French compaignon, from Vulgar Latin *compāniō, a compound noun formed from Latin com- ‘with’ and pānis ‘bread’. The Old French stem compaign- also formed the basis of compaignie, from which English gets company .
Compare MATE. The companion of companionway ‘stairway on a ship’  is of similar but distinct origin. It comes ultimately from Vulgar Latin *compānia, a compound noun meaning ‘what one eats with bread’, formed from Latin com- ‘with’ and pānis ‘bread’. In Italian this became campagna ‘provisions’, which was used in the phrase camera della campagna ‘(ship’s) storeroom’.
The meaning of the phrase eventually passed to campagna on its own, and was carried via Old French compagne to Dutch kompanje, which meant ‘quarterdeck’. English borrowed this, and adapted it to the more familiar English pattern companion. => company, pannier
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 (compare Gothic gahlaiba "messmate," from hlaib "loaf of bread"). Replaced Old English gefera "traveling companion," from faran "go, fare."