conclusory (adj.)

early 14c., "confute or frustrate an opponent in argument, end an argument by winning it," from Latin concludere "to shut up, enclose," from assimilated form of com "together" (see con-) + -cludere, combining form of claudere "to shut" (see close (v.)).

Meanings "reach a mental determination, deduce; infer or determine by reason" are from late 14c., a sense also in Latin. General sense of "bring to an end, finish, terminate," and intransitive sense of "come to an end" are from late 14c. Meaning "settle, arrange, determine finally" is from early 15c. Sometimes in Middle English it was used in the etymological sense, "shut in" (late 14c.). Related: Concluded; concluding.

adjective and noun suffix, "having to do with, characterized by, tending to, place for," from Middle English -orie, from Old North French -ory, -orie (Old French -oir, -oire), from Latin -orius, -oria, -orium.

Latin adjectives in -orius, according to "An Etymological Dictionary of the French Language," tended to "indicate a quality proper to the action accomplished by the agent; as oratorius from orator; laudatorius from laudator. The neuter of these adjectives was early employed as a substantive, and usually denoted the place of residence of the agent or the instrument that he uses; as praetorium from praetor; dormitorium from dormitor; auditorium, dolatorium.

"These newer words, already frequent under the Empire, became exceedingly numerous at a later time, especially in ecclesiastical and scholastic Latin; as purgatorium, refectorium, laboratorium, observatorium, &c." [transl. G.W. Kitchin, Oxford, 1878]