upset (v.)
mid-15c., "to set up, fix," from up (adv.) + set (v.). Similar formation in Middle Dutch opsetten "set up, propose," German aufsetzen. Modern sense of "overturn, capsize" (1803) is that of obsolete overset. In reference to the stomach, from 1834. Meaning "to throw into mental discomposure" is from 1805. Related: Upsetting.
upset (n.)
early 15c., "insurrection," from upset (v.). Meaning "overturning of a vehicle or boat" is recorded from 1804.
upset (adj.)
early 14c., "erected," past participle adjective from upset (v.). From 1805 as "distressed."