acrimonious (adj.)

1540s, "quality of being sharp or pungent in taste," from French acrimonie or directly from Latin acrimonia "sharpness, pungency of taste," figuratively "acrimony, severity, energy," abstract noun from acer "sharp" (fem. acris), from PIE root *ak- "be sharp, rise (out) to a point, pierce") + -monia suffix of action, state, condition (see -mony). Figurative extension to personal sharpness or bitterness is by 1610s.

1712, "sharp and bitter to the taste," formed irregularly (perhaps by influence of acrimonious) from Latin acer (fem. acris) "sharp to the senses, pungent, bitter; eager, fierce," also figuratively, of qualities, "active, ardent, spirited," also "hasty, quick, passionate;" of mind "violent, vehement; subtle, penetrating," from PIE *akri- "sharp," from root *ak- "be sharp, rise (out) to a point, pierce." Of feelings, temper, etc., in English from 1781. The -id suffix probably is in imitation of acid. Acrious (1670s) is a correct formation, but seldom seen. Related: Acridly.