carrier (n.)

late 14c., "one who or that which conveys," agent noun from carry (v.). Meaning "person or animal that carries and disseminates infection without suffering obvious disease" is from 1899; genetic sense is 1933. As a short form of aircraft carrier it dates from 1917. Carrier-pigeon, one of a breed trained to convey from one place to another written messages tied to its leg (also homing-pigeon), is from 1640s.