*leikw-

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.

1640s, "left, abandoned by the owner or guardian," from Latin derelictus "solitary, deserted," past participle of dereliquere "to abandon, forsake, desert," from de- "entirely" (see de-) + relinquere "leave behind, forsake, abandon, give up," from re- "back" (see re-) + linquere "to leave," from PIE root *leikw- "to leave."

Originally especially of vessels abandoned at sea or stranded on shore. Of persons, "unfaithful, neglectful of responsibility," by 1864. As a noun, "property which is abandoned," from 1660s. As "person abandoned or forsaken," 1728.