Unguilty is from un- ('not') + guilty, from Old English gyltig ('offending, guilty'), from gylt ('crime, sin, fault'), of uncertain further origin. Important recorded forms include un- (Old English), gyltig (Old English), and gylt (Old English). Morphologically, the un- element marks negation, reversal, removal, or deprivation, while the base supplies the action, quality, or state being denied or undone. The modern sense continues the older lexical line without requiring a separate origin. In current use it covers free from guilt; innocent. The wider family includes related words such as guilt, guilty, and guiltless.