convoy (n.)

1550s, "the act of guiding or escorting for protection," from obsolete verb convoy "to accompany on the way for protection" (late 14c.), from Old French convoiier, from Vulgar Latin *conviare, literally "go together on the road," from assimilated form of Latin com "with, together" (see con-) + via "way, road" (from PIE root *wegh- "to go, move, transport in a vehicle").

Compare convey. The meaning "an escort, an accompanying and protecting force" is from 1590s; sense transferred by c. 1600 to "train of ships or wagons carrying munitions or provisions in wartime under protection of escort."