"post, letters," c.1200, "a traveling bag," from Old French male "wallet, bag, bundle," from Frankish *malha or some other Germanic source, from Proto-Germanic *malho- (cf. Old High German malaha "wallet, bag," Middle Dutch male "bag"), from PIE *molko- "skin, bag." Sense extension to "letters and parcels" (18c.) is via "bag full of letter" (1650s) or "person or vehicle who carries postal matter" (1650s). In 19c. England, mail was letters going abroad, while home dispatches were post. Sense of "personal batch of letters" is from 1844, originally American English.