The Scotland/Northern Ireland idiom for gagging without vomiting.
NOTE: The idiom is *the*
dry boak. It it never *a*
dry boak.
It is from this idiom that the word boak escaped to take on a life of its own (along with the alternate spelling boke) -- with some
people using boak (or boke) to mean "the dry boak," and others meaning normal vomiting.
"It would huv gied
ye the
dry boak tae hear them sookin up tae him, aw sweetie sweetie." (Anne
Donovan, Hieroglyphics: And Other Stories, 2001)