Words for "error" in most Indo-European languages originally meant "wander, go astray" (for example Greek plane in the New Testament, Old Norse villa, Lithuanian klaida, Sanskrit bhrama-), but Irish has dearmad "error," from dermat "a forgetting."
"deserving censure, blameworthy," late 13c., coupable, from Old French coupable (12c., Modern French coupable), from Latin culpabilis "worthy of blame," from culpare "to blame," from culpa "crime, fault, blame, guilt, error." De Vaan writes that this might be from a PIE root *kuolp- "to bend, turn" (source also of Greek kolpos "bosom, lap;" see gulf (n.)). According to his sources, "The original meaning of culpa is 'a state of error' rather than 'an error committed'." English (and for a time French) restored the first Latin -l- in later Middle Ages. Related: Culpably; culpableness.