Having the character or qualities associated with gall; bold, impudent, or marked by audacious disrespect.
From 'gall' (meaning both the fluid secreted by the liver and figuratively, boldness or impudence) plus the adjectival suffix '-ish' (meaning 'somewhat like' or 'having the quality of').
The word 'gall' has a split personality in English—it means the bitter bile in your body AND it means having the nerve to do something outrageous, so 'gallish' behavior is literally doing something as offensive as actual bile tastes.
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