Abbott-Smith Manual Greek Lexicon
ἀνεξιχνίαστος (G421)
2 † ἀνεξιχνίαστος , -ον ( ἀ- neg., ἐξιχνιάζω , to track out ; ἴχνος ), [in LXX: Jb 5:9 9:10 34:24 ( חֵקֶר אֵין )*;] that cannot be traced out : Ro 11:33 , Eph 3:8 (MM, VGT , s.v.).†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain