early 14c. (late 13c. as Anglo-Latin foragium) "food for horses and cattle, fodder," from Old French forrage "fodder; foraging; pillaging, looting" (12c., Modern French fourrage), from fuerre "hay, straw, bed of straw; forage, fodder" (Modern French feurre), from Frankish *fodr "food" or a similar Germanic source, from Proto-Germanic *fodram (source of Old High German fuotar, Old English fodor; see fodder). Meaning "a roving in search of provisions" in English is from late 15c. Military forage cap attested by 1827.
early 15c., "to plunder, pillage," from forage (n.) or from Middle French fourrager. Meaning "hunt about for" is from 1768. Related: Foraged; foraging.