Dictionary entry

κρυφαῖος

G. Abbott-Smith's A Manual Greek Lexicon of the New Testament

κρυφαῖος, -αία, -αῖον

(< κρύφα = κρυφῆ), [in LXX for מִסְתָּר, Je 23:24, al.;]

hidden, secret: ἐν τῷ κ., Mt 6:18.†