英语词源字典 - 在线词源网站

betrayer (n.)[betrayer 词源字典]: 1520s, agent noun from betray (v.).[betrayer etymology, betrayer origin, 英语词源]
frayed (adj.): "worn by rubbing," 1814, past participle adjective from fray (v.).
prayer (n.): c. 1300, from Old French prier "prayer, petition, request" (12c., Modern French prière), from Medieval Latin precaria "petition, prayer," noun use of Latin adjective precaria, fem. of precarius "obtained by prayer, given as a favor," from precari "to ask, beg, pray" (see pray). Related: Prayers.

Prayer-book attested from 1590s; prayer-meeting from 1780. To not have a prayer "have no chance" is from 1941.
prayerful (adj.): 1620s, from prayer + -ful. Related: Prayerfully; prayerfulness.