betray: [13] Betray is an English formation based on the Old French verb traïr ‘betray’, which came from Latin tradere ‘hand over, deliver up’ (originally a compound formed from trans- ‘across’ and dāre ‘give’). The noun formed from tradere was trāditiō, from which English gets, directly, tradition, and indirectly, via Old French and Anglo-Norman, the appropriate treason. => tradition, treason
betray (v.)
late 13c., bitrayen "mislead, deceive, betray," from be- + obsolete Middle English tray, from Old French traine "betrayal, deception, deceit," from trair (Modern French trahir) "betray, deceive," from Latin tradere "hand over," from trans- "across" (see trans-) + dare "to give" (see date (n.1)). Related: Betrayed; betraying.