Abbott-Smith Manual Greek Lexicon
αἰφνίδιος (G160)
2 ** αἰφνίδιος (in Lk 21:34 , ἐφν- WH; v. M, Pr. , 35), -ον ( αἴφνης = ἄφνως , suddenly ), [in LXX: Wi 17:15 , II Mac 14:17 , III Mac 3:24 *;] sudden , unexpected : Lk 21:34 , I Th 5:3 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain