whilom (adv.)youdaoicibaDictYouDict[whilom 词源字典]
"at time past" (archaic), c. 1200, from Old English hwilum "at times," dative case of while (q.v.). As a conjunction from 1610s. Similar formation in German weiland "formerly."[whilom etymology, whilom origin, 英语词源]