late 15c., "one who fails to perform a duty or discharge an obligation," also, generally, "an offender against the law," a noun use from Latin delinquentum (nominative delinquens), present participle of delinquere "to fail; be wanting, fall short; do wrong, transgress, offend," from de- "completely" (see de-) + linquere "to leave" (from PIE root *leikw- "to leave"). As an adjective, "failing or neglectful in duty," from c. 1600 in English.
