caster (n.1)youdaoicibaDictYouDict[caster 词源字典]
"person or thing that casts," late 14c. (also sometimes castor), agent noun from cast (v.). Meaning "pepper shaker, small perforated container" is from 1670s, on notion of "throwing."[caster etymology, caster origin, 英语词源]
caster (n.2)youdaoicibaDictYouDict
"wheel and swivel attached to furniture," 1748, agent noun from cast (v.) in the old sense of "turn." Also sometimes castor.