"Boak" is a Scots word that means "retch" (or vomit), and like retch it can be used as a verb, i.e. "that makes me want to boak" means "that makes me want to retch", but it can also be used as a noun, as in the phrase "that gies (gives) me the boak", which means the same thing, effectively changing boak from a verb meaning "retch" to a noun meaning "the desire to retch" or "the impulse to retch" More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.