professional (adj.)youdaoicibaDictYouDict[professional 词源字典]
early 15c., of religious orders; 1747 of careers (especially of the skilled or learned trades from c. 1793); see profession. In sports, opposed to amateur, from 1846. Related: Professionally.[professional etymology, professional origin, 英语词源]
professional (n.)youdaoicibaDictYouDict
"one who does it for a living," 1798, from professional (adj.).