Strong’s Greek
G160 — aiphnidios
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
αἰφνίδιος
aiphnidios — pronounced aheef-nid'-ee-os
from a compound of 1 (as a negative particle) and 5316 (compare 1810) (meaning non-apparent); unexpected, i.e. (adverbially) suddenly:--sudden, unawares. see GREEK for 1 see GREEK for 5316 see GREEK for 1810
2 occurrences in the KJV.
Luke 21:34
And take heed to yourselves, lest at any time your hearts be overcharged with surfeiting, and drunkenness, and cares of this life, and so that day come upon you unawares.
1 Thessalonians 5:3
For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.