caster (n.1)

also sometimes castor, "person or thing that casts," late 14c., agent noun from cast (v.). Meaning "pepper shaker, small perforated container" is from 1670s, on notion of "throwing" the powder, liquid, etc., when needed.

"small wheel and swivel attached to the leg of a piece of furniture," 1748, agent noun from cast (v.) in the old sense of "turn." Also sometimes castor.