the.com/gall

means Gall is bold, brazen nerve — the shameless audacity to do something presumptuous without a flicker of embarrassment.

from From Old English 'gealla,' meaning bile, the bitter fluid the liver produces — same root as 'gallbladder.' Bile was long thought to govern temperament in old humor-based medicine: too much of it made you bitter, rancorous, or recklessly bold. 'Gall' the organ-fluid and 'gall' the nerve are the same word — the sense just curdled from the physical bitterness into the figurative nerve of someone bitter enough not to care what you think.