Yours, Etc.: Origins and Uses of 8 Sign-Offs
mid-15c., "box, case," from Old French tronc "alms box in a church" (12c.), also "trunk of a tree, trunk of the human body," from Latin truncus, originally "mutilated, cut off." The meaning "box, case" is likely to be from the notion of the body as the "case" of the organs. English acquired the other two senses of the Old French in late 15c.: "main stem of a tree" and "torso of a human body." The sense of "luggage compartment of a motor vehicle" is from 1930. The use in reference to an elephant's snout is from 1560s, perhaps from confusion with trump (short for trumpet). Railroad trunk line is attested from 1843; telephone version is from 1889.
The body excluding the head and limbs.
The main stem of a blood vessel or nerve apart from the branches.
A large collecting lymphatic vessel.