Meaning

adjective characterized by iniquity; wicked because it is believed to be a sin

adjective having committed unrighteous acts

adjective far more than usual or expected

originFrom Middle English synful, senful, sunful, from Old English synful (“sinful, guilty, wicked, corrupt”), equivalent to sin + -ful. Compare Dutch zondevol (“sinful”), German sündevoll (“sinful”), Danish syndefuld (“sinful”), Swedish syndfull (“sinful”), Icelandic syndfullur (“sinful”).

Etymology from Wiktionary, CC BY-SA 3.0