püf noktası

Etymology
From, from a folk tale about either a pottery or glassblowing apprentice impatiently wanting to open his own shop, but his master not giving him his leave because the apprentice hadn't yet learned "the puff point" of the art, supposedly where one gently blows on the tiny air bubbles formed in the material to pop them before it has dried to prevent the item from cracking or breaking easily.

Noun

 * 1)  The most important part of a thing that separates the experienced and others; the secret, the trick, the crux of the matter.