late 14c., "put down by force, conquer," a sense now obsolete, from Old French depresser "to press down, lower," from Late Latin depressare, frequentative of Latin deprimere "press down," from de "down" (see de-) + premere "to press, hold fast, cover, crowd, compress" (from PIE root *per- (4) "to strike").
Meaning "push down physically, press or move downward" is from early 15c.; that of "deject, make gloomy, lower in feeling" is from 1620s; economic sense of "lower in value" is from 1878.
word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).
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Harper, D. (n.d.). Etymology of depressive. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/depressive