#modernhebrewtips
I get these in my email all the time and I it occurred to me I should be sharing them. So here it goes.
עַל קוֹצִים
Al Kotzim

Literally: On thorns
Idiomatically: On edge

This modern phrase is basically slang. The word "kotzim" is found in Genesis (3:18), and is part of God's curse on Adam and all of humankind. A "kotz" in general refers to any kind of thorn. Now if someone tries to sit on a thorn bush - he won’t very comfortable , and as such he will be well, on edge , hence the phrase.
A more popular thorn phrase is "kotz betachat" קוץ בתחת) ( which is gently translated into English as a thorn in one's side. In Hebrew we use a more descriptive word that refers to a body part further south.

הוא ישב על קוצים עד שהוא קיבל את התשובות של המבחנים
"Hu yashav al kotzim ad shehu kibel et hateshuvot shel hamivchanim." He was on edge until he received the results of the test. Anyone have a pair of tweezers?