2 occurrences in 2 dictionaries

Reference: Infidel

Hastings

This word has more force now than formerly. In AV it signifies no more than 'unbeliever.' It occurs in 2Co 6:15; 1Ti 5:8 (RV 'unbeliever' in both). So 'infidelity' in 2Es 7:44 is simply 'unbelief' (Lat. incredulitas).