invalid (adj.1) Look up invalid at
"not strong, infirm," also "infirm from sickness, disease, or injury", 1640s, from Latin invalidus "not strong, infirm, impotent, feeble, inadequate," from in- "not" (see in- (1)) + validus "strong" (see valid). With pronunciation from French invalide (16c.).
invalid (n.) Look up invalid at
"infirm or sickly person," 1709, originally of disabled military men, from invalid (adj.1). In Paris, Invalides is short for Hôtel des Invalides, home for old and disabled soldiers in the 7th arrondissement of Paris.
invalid (adj.2) Look up invalid at
"of no legal force," 1630s, from special use of Latin invalidus "not strong, weak, feeble" (see invalid (adj.1)).