1640s, "unreasonably or unjustly burdensome," from Medieval Latin oppressivus, from oppress-, past participle stem of opprimere "press against, press together, press down;" figuratively "crush, put down, subdue, prosecute relentlessly" (see oppress). Sense of "inclined to oppress, tyrannical" is from 1712; that of "heavy, overwhelming" (of grief, woe, heat, etc.) is by 1712. Related: Oppressively; oppressiveness.
Old English, present-participle adjective from grind (v.). Meaning "oppressive, burdensome" is from 1580s. The verbal noun is from mid-14c.
"burdensome, troublesome," late 14c., from Old French onereus, honereus (14c., Modern French onéreux) and directly from Latin onerosus "burdensome, heavy, oppressive," from onus (genitive oneris) "a burden" (see onus). Related: Onerously; onerousness.
1540s, "influential, respected; marked by weighty dignity," from French grave (Old French greve "terrible, dreadful," 14c.), from Latin gravis, "heavy, ponderous, burdensome, loaded; pregnant;" of matters, "weighty, important;" of sounds, "deep, low, bass;" figuratively "oppressive, hard to bear, troublesome, grievous," from PIE root *gwere- (1) "heavy."
In English, the sense "solemn, sober" is from 1580s; of immaterial things, "important, serious" 1590s. Greek barys (opposed to kouphos) also was used figuratively, of suffering, sorrow, sobbing, and could mean "oppressive, burdensome, grave, dignified, impressive." The noun meaning "accent mark over a vowel" is c. 1600, from French.
late 14c., rebellen, "rise up against (a ruler, one's government, etc.); be insubordinate," from Old French rebeller (14c.) and directly from Latin rebellare "to revolt" (see rebel (adj.)). In general, "make war against anything deemed oppressive" from late 14c. Related: Rebelled; rebelling.
late 14c., from Old French injustice "unfairness, injustice" (14c.), from Latin iniustitia "unfairness, injustice," from iniustus "unjust, wrongful, unreasonable, improper, oppressive," from in- "not" (see in- (1)) + iustus "just" (see just (adj.)). Injust (adj.) is attested from late 15c., from French, but unjust is the usual English word.