jist, gist or gyst? And how to say it?

Main Entry: gist Pronunciation: 'jist Function: noun
Etymology: Anglo-French, in the phrase laccion gist the action lies or is based (on), from gisir to lie (of process), from Old Frenchgesir to lie, ultimately from Latin jacere
: the ground or foundation of a legal action without which it would not be sustainable

The word is spelled "gist." It comes from the French word "gesir," a verb meaning "to lie." In 1688, the word entered the English language as a legal term, in the sense that something "lies in the center" or is the heart of the matter or case. It remained a legal term only for a number of years before it was adopted into general usage, explains Ted Nesbitt.

In 1823, Corbett used the word in writing for the first time in a non-legal sense. "This is the gist," he meant "This is the heart of the matter, or this is the central focus."

So, the word has come to mean the very heart of something, particularly if that "something" is very complicated. Let's suppose that a committee has been discussing a problem for many hours and still has not clearly identified the problem. Then, some brilliant person -- probably not the committee's chair person -- says quite succinctly, "Here is the gist of the problem," and then summarizes exactly what the problem is. THAT is what is meant by "gist."

From "The Oxford English Dictionary" -- the Bible of the etymological field:

[a. OF. gist (F. gît), 3 sing. pres. ind. of gésir to lie, gésir en to consist in, depend on, used in the AF. law phrase (cest) action gist, ‘(this) action lies', which occurs 1502-3 in Kelvey's Rep. (1688) lf. 50a, and is common in law-books.]
1. Law. The real ground or point (of an action, indictment, etc.).

2. The substance or pith of a matter, the essence or main part.