FROM STRONG’S GREEK DICTIONARY (1890)

Strong’s Greek Dictionary (1890) — public domain, printed whole.

apistos ἄπιστος — ap'-is-tos — from 1 (as a negative particle) and 4103; (actively) disbelieving, i.e. without Christian faith (specially, a heathen); (passively) untrustworthy (person), or incredible (thing):--that believeth not, faithless, incredible thing, infidel, unbeliever(-ing).

see GREEK for 1

see GREEK for 4103