mid-14c., discussioun, "examination, investigation, judicial trial," from Old French discussion "discussion, examination, investigation, legal trial" and directly from Medieval Latin discussionem (nominative discussio) "examination, discussion," in classical Latin, "a shaking," noun of action from past-participle stem of discutere "strike asunder, break up," in Late Latin and Medieval Latin also "to discuss, examine, investigate," from dis- "apart" (see dis-) + quatere "to shake" (see quash).
Meaning "a talking over, debating" in English first recorded mid-15c. Sense evolution in Latin appears to have been from "smash apart" to "scatter, disperse," then in post-classical times (via the mental process involved) to "investigate, examine," then to "debate."
"debatable, subject to discussion," by 1650s, from moot case (1570s), earlier simply moot (n.) in the specialized sense "discussion of a hypothetical law case" (1530s) in law student jargon. The reference is to students gathering to test their skills in mock cases.
"to beat soundly," 1630s (in an Oriental travel narrative), probably ultimately from Arabic darb "a beating," from daraba "he beat up" (see discussion in OED). Related: Drubbed; drubbing.
public place of assembly in ancient Athens, where the people met for the discussion of political affairs of the state, from Greek pnyx, which is probably from pyknos "dense, solid; numerous; packed, crowded," a word of uncertain origin.