Abbott-Smith Manual Greek Lexicon
λάθρᾳ (G2977)
4 λάθρᾳ (Att.; in Hom., -ρῃ , Rec. -ρα ), adv. , [in LXX chiefly for בַּסֵּתֶר ;] secretly : Mt 1:19 2:7 , Mk 5:33 (WH, mg.), Jo 11:28 , Ac 16:37 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain