Strong's:ὦ as a sign of the vocative case, O; as a note of exclamation, ohDerivation: a primary interjection;KJV Usage: O.
TBESG:ὦoh!G:Intj ὦ interj., with vocat., O; __(a) in simple address (less freq. than in cl.; M, Pr., 71); Refs Act.1:1 18:14 27:21, Rom.2:1, 3 9:20, 1Ti.6:20; expressing reproof, Jas.2:20; __(b) in exclamations of surprise, etc.: Refs Mat.15:28, Luk.24:25, Act.13:10, Rom.11:33, Gal.3:1; with nom. (Bl., § 33, 4), Refs Mat.17:17, Mrk.9:19, Luk.9:41.† (AS)