** ἀΐδιος, -ον (< ἀεί), [in LXX: Wi 7:26, IV Mac 10:15*;] everlasting (freq. in Inscr.; MM, VGT, s.v.): Ro 1:20, Ju 6.†
SYN.: αἰώνιος, also freq. in Inscr. (Deiss., BS, 363 J. The etymological distinction between the meanings of the two words seems not to be retained in late Greek (v. Thayer, s.v., αἰώνιος; cf. Cremer, 79, 611).
Henry George Liddell, Robert Scott, A Greek-English Lexicon, ἀΐδιος
katabiblon.com Wiki Lexicon of the Greek New Testament and Concordance, ἀΐδιος