gall (n.2)
"sore on skin caused by rubbing or chafing," Old English gealla "painful swelling, sore spot on a horse," probably from Latin galla "gall, lump on plant," originally "oak-gall" (see gall (n.3)). Perhaps from or influenced by gall (n.1) on notion of "poison-sore." Meaning "bare spot in a field" (1570s) is probably the same word. German galle, Dutch gal also are said to be from Latin.
gall (v.)
"to make sore by chafing," mid-15c., from gall (n.2). Earlier "to have sores, be sore" (early 14c.). Figurative sense of "harass, vex, irritate, chafe the spirit of," is from 1570s. A past-participle adjective gealled is found in Old English, but OED says this is from the noun. Related: Galled; galling.
gall (n.3)
"excrescence on a plant caused by the deposit of insect eggs," especially on an oak leaf, late 14c., from Latin galla "oak-gall," which is of uncertain origin. They were harvested for use in medicines, inks, dyes.
gall (n.1)
"bile, liver secretion," Old English galla (Anglian), gealla (West Saxon) "gall, bile," from Proto-Germanic *gallon "bile" (source also of Old Norse gall "gall, bile; sour drink," Old Saxon galle, Old High German galla, German Galle), from PIE root *ghel- (2) "to shine," with derivatives denoting "green, yellow," and thus "bile, gall." Informal sense of "impudence, boldness" first recorded American English 1882; but meaning "embittered spirit, rancor" is from c. 1200, from the medieval theory of humors.