late 14c., from Old French transgression "transgression," particularly that relating to Adam and the Fall (12c.), from Late Latin transgressionem (nominative transgressio) "a transgression of the law," in classical Latin, "a going over, a going across," noun of action from transgressus, past participle of transgredi "step across, step over; climb over, pass, go beyond," from trans- "across" (see trans-) + gradi (past participle gressus) "to walk, go" (see grade, n.). Geological sense is from 1882.