packet (n.)

mid-15c., paket, "a little package or parcel" (late 12c. as a surname), "in earliest use applied to a parcel of letters or dispatches, and esp. to the State parcel or 'mail' of dispatches to and from foreign countries" [OED], from Middle English pak "bundle" (see pack (n.)) + diminutive suffix -et; perhaps modeled on Anglo-French pacquet (Old French pacquet), which ultimately is a diminutive of Middle Dutch pak or some other continental Germanic word cognate with the English one. A packet boat (1640s) originally was one that carried mails from country to country or port to port, then generally a vessel starting at regular dates and appointed times. In data transmission, packet-switching is attested from 1971.