hysterical (adj.)
1610s, "characteristic of hysteria," from Latin hystericus "of the womb," from Greek hysterikos "of the womb, suffering in the womb," from hystera "womb" (see hysteria). Meaning "very funny" (by 1939) is from the notion of uncontrollable fits of laughter. For "inclined to hysteria," American English formerly had the colloquial hystericky (1792). Related: Hysterically.