FAITHLESS.Wherever this word occurs in AV [Note: Authorized Version.] , it means, not untrustworthy, but unbelieving, just as in the Merchant of Venice Shylock is called a faithless Jew, simply because he was an unbeliever in Christ.
Hastings' Dictionary of the Bible
Edited by James Hastings, D.D. Published in 1909
fāth?les: The translation of ἄπιστος, ápistos, ?without faith,? having the sense of ?unbelieving,? ?disbelieving.? Jesus upbraids the people, ?O faithless and perverse generation!? (Mat_17:17; Mar_9:19; Luk_9:41); He says to Thomas, ?Be not faithless, but believing? (Joh_20:27); the Revised Version (British and American) adds, ?If we are faithless,? instead of ?believe not? (2Ti_2:13); compare 1Co_7:12-15; 1Co_10:27; 1Co_14:22, 1Co_14:24, etc.; Tit_1:15. In Luk_12:46 apistos has the sense of ?unfaithful,? so the Revised Version (British and American); perhaps also Rev_21:8, ?unbelieving.?
International Standard Bible Encyclopedia
PRINTER 1915.