frig (v.)youdaoicibaDictYouDict[frig 词源字典]
"to move about restlessly," mid-15c., perhaps a variant of frisk (q.v.). As a euphemism for "to fuck" it dates from 1550s (frigging); from 1670s as "to masturbate." Related: Frigged; frigging.[frig etymology, frig origin, 英语词源]