(n.) a bird’s regular perching spot
To most English speakers, the word gist will probably be familiar as a word for the nub or core point of an argument or issue: to get the gist of something is to thoroughly understand it.
In this context, gist was adopted into English from Anglo-Norman judicial language, falling into more common use via various stock legalese phrases, like l’action gist, that date from a post-Conquest era when French was still the principal language of English courts.
Etymologically, gist (the Norman equivalent of modern French gît, or gîte) comes from the verb gésir, literally meaning ‘to lie’; l’action gist, ultimately, means ‘the action lies’.
Once upon a time, however, that etymological meaning earned the word gist a handful of other meanings in English. In medieval times a gist was a stop on a journey or tour—particularly one undertaken by a monarch, or some similarly important figure or dignitary. In Middle English, a gist was a break for nourishment or refreshment. And, in the 1500s, it became a word for a bird’s frequently-used perching spot.
In that latter sense, a gist is literally a bird’s ‘lying’ spot: a place where it often perches or pauses—perhaps to feed or hunt from—or else where it can frequently be seen or encountered. This use of the word has been unearthed in print way back in 1545 by the Oxford English Dictionary, a full two centuries before the use of gist to mean the point or main issue of an argument became established in the early 1700s.