From the same as hagios; properly, clean, i.e. (figuratively) innocent, modest, perfect -- chaste, clean, pure.
see GREEK hagios
1. exciting reverence, venerable, sacred: πῦρ καί ἡ σποδός, 2 Macc. 13:8; Euripides, El. 812.
2. pure (Euripides, Or. 1604 ἁγνός γάρ εἰμί χεῖρας, ἀλλ' οὐ τάς φρένας, Hipp. 316f, ἁγνάς ... μίασμα);
a. pure from carnality, chaste, modest: Titus 2:5; παρθένος an unsullied virgin, 2 Corinthians 11:2 (4 Macc. 18:7).
b. pure from every fault, immaculate: 2 Corinthians 7:11; Philippians 4:8; 1 Timothy 5:22; 1 Peter 3:2; 1 John 3:3 (of God (yet cf. ἐκεῖνος 1 b.)); James 3:17. (From Homer down.) (Cf. references under the word ἅγιος, at the end; Westc. on 1 John 3:3.)