laches (n.) Look up laches at Dictionary.com
"negligence in performance of legal dute," 1570s, earlier simply "slackness, negligence, want of zeal" (late 14c.), from Anglo-French laches, Old French lachesse, from Old French lasche (Modern French lâche), verbal adjective from lascher, from Vulgar Latin *lascare, classical laxare, from laxus (see loose). Compare riches.