An Etymological Dictionary of Astronomy and Astrophysics

1. An instance of the occurrence, or existence of something.
   

2. A set of circumstances or conditions.
   

3. Grammar: An inflectional form of a noun, pronoun, or adjective indicating its grammatical relation to other words.

Etymology (EN): M.E. cas, from O.Fr. cas “an event, happening, situation,” from L. casus “a chance, occasion, opportunity; accident,” literally “a falling,” from cadere “to fall, sink, settle down” (Sp. caer, caida); Sp. caso; It. caso; Port. caso;
PIE root *kad- “to fall;” cf. Skt. śad- “to fall down;” Pers. kat, as below.

Etymology (PE): Kâté, from Iranian dialects/languages kat- “to fall” (with extension of the first vowel), as Laki: katen “to fall,” kat “he/she fell,” beko “fall!” (an insult); katyâ “fallen;” Lori: kat “event, error;” Kurd. (Soriani): kawtin “to fall, befall,” kett “fallen;” Kurd. (Kurmanji): da.ketin “to fall down;” Lârestâni: kata “to fall;” Garkuyeyi: darkat, varkat “he/she fell (sudden death);” Gilaki (Langarud, Tâleš): katan “to fall,” bakatam “I fell,” dakatan “to fall (in a marsh, in a pit),” vakatan “to fall from tiredness, be exhausted,” fakatan “to fall from (i.e., lose) reputation;” Tabari: dakətə “fallen,” dakətən “to crash down,” dakət.gu “stray cow;” Proto-Iranian *kat- “to fall;” cf. L. cadere, as above. Alternatively, from Proto-Ir. *kap-, *kaf- “to (be)fall, strike (down);” cf. Baluci kapag, kafag “to fall,” kapt “(past tense) fell;” Bampuri kapte “fallen;” Kurd. (Sanandaj) kaften “to fall;” Gilaki jekaftan “to fall;” Nâyini derkaftan “to fall down.”