depreciatory (adj.)

mid-15c., "to undervalue, under-rate," from Latin depretiatus, past participle of depretiare "to lower the price of, undervalue," from de "down" (see de-) + pretium "price" (see price (n.)). From 1640s in transitive sense of "lessen the value of, to lower in value." Intransitive sense of "to fall in value, become of less worth" is from 1790. Related: Depreciated; depreciating.

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]