"state of affairs," early 13c., from O.Fr. cas "an event," from L. casus "a chance," lit. "a falling," from cas-, pp. stem of cadere "to fall, sink, settle down, decline, perish" (used widely: of the setting of heavenly bodies, the fall of Troy, suicides), from PIE base *kad- "to lay out, fall or make fall, yield, break up" (cf. Skt. sad- "to fall down," Armenian chacnum "to fall, become low," perhaps also M.Ir. casar "hail, lightning"). The notion being "that which falls" as "that which happens." Widespread extended senses in law, medicine, grammar, etc. In case "in the event" is recorded from mid-14c. Case history is from 1912, originally medical; case study is from 1933, originally legal.
"receptacle," c.1300, from O.N.Fr. casse, O.Fr. chasse, from L. capsa "box," from capere "to take, hold" (see capable). The verb meaning "examine, inspect" (usually prior to robbing) is Amer.Eng. slang first recorded 1915. Staircase is from 1663. Artillery sense is from 1667, from case-shot "small projectiles put in cases" (1625). Reference in the printing trade (first recorded 1588) to the two trays where compositors keep their types in separate compartments for easy access led to upper case for capitals and lower case for small letters.