Original meaning
διάβολ-ος, ον,
I slanderous, backbiting, γραῦς Men. 878, cf. Phld. Lib. p.24O.: Sup. -ώτατος Ar. Eq. 45; διάβολόν τι, aliquid invidiae, And. 2.24; τὸ δ. Plu. 2.61d.
II Subst., slanderer, Pi. Fr. 297, Arist. Top. 126a31, Ath. 11.508d; enemy, LXX Ezr_7:4, LXX Ezr_8:1 : hence, = Sâtân, ib. 1Ch_21:1; the Devil, Mat_4:1, etc.
III Adv. -λως injuriously, invidiously, Th. 6.15; χρῆσθαί τινι Procop. Arc. 2.
Liddell & Scott Greek Lexicon
διάβολος, διάβολον (διαβάλλω which see), prone to slander, slanderous, accusing falsely, (Aristophanes, Andocides (), Plutarch, others): 1Ti_3:11; 2Ti_3:3; Tit_2:3; as a substantive, ὁ διάβολος, a calumniator, false accuser, slanderer, (see κατηγορέω, at the end) (Xenophon, Ages. 11, 5; (Aristotle, others)): the Sept. Est_7:4; Est_8:1. In the Bible and in ecclesiastical writings ὁ διάβολος (also διάβολος without the article; cf. Winers Grammar, 124 (118); Buttmann, 89 (78)) is applied κατ' ἐξοχήν to the one called in Hebrew äÇùÈÌÒèÈï, ὁ σατανᾶς (which see), viz., Satan, the prince of demons, the author of evil, persecuting good men (Job_1:1-22; Zec_3:1 ff, cf. Rev_12:10), estranging mankind from God and enticing them to sin, and afflicting them with diseases by means of demons who take possession of their bodies at his bidding; the malignant enemy of God and the Messiah: Mat_4:1; Mat_4:5,(); ; Luk_4:2,( R L, ); ; Joh_13:2; Act_10:38; Eph_4:27; Eph_6:11; 1Ti_3:6; 2Ti_2:26; Heb_2:14; Jas_4:7; 1Pe_5:8; Jud_1:9; Rev_2:10; Rev_12:9; Rev_12:12; Rev_20:2; Rev_20:10; (Wis_2:24; (cf. Psa_108:6 (); 1Ch_21:1)). Men who resemble the devil in mind and will are said εἶναι ἐκ τοῦ διαβόλου to be of the devil, properly, to derive their origin from the devil, tropically, to depend upon the devil in thought and action, to be prompted and governed by him: Joh_8:44; 1Jn_3:8; the same are called τέκνα τοῦ διαβόλου, children of the devil, 1Jn_3:10; υἱοί τοῦ διαβόλου, sons of the devil, Act_13:10, cf. Mat_13:38; Joh_8:38; 1Jn_3:10. The name διάβολος is figuratively applied to a man who, by opposing the cause of God, may be said to act the part of the devil or to side with him: Joh_6:70, cf. Mat_16:23; Mar_8:33. (Cf. σαταν at the end.)
J H Thayer, Greek Lexicon