Language Of Confusion: Ak-!, Part I

What is ak-? Besides the noise you make when something is stuck in your throat? It’s a Proto Indo European root meaning to be sharp, rise to a point, or pierce. And the words descended from it are varied and bizarre. As usual.
 
This is actually the origin word for acid. It showed up in the early seventeenth century and meant vinegar-tasting, while an acid, like in chemistry, didn’t show up until the late seventeenth century, and its definition was refined over the next century as more about chemistry was refined. It’s from either the French acide or classical Latin acidus, which means acid, sour, or sharp. And yeah, that figurative sense of a biting smell is why it’s from the PIE word for sharp.
 
Speaking of biting, there’s also acerbic, another word I enjoy using. It didn’t show up until 1865, so remember that for your Civil War fics—though acerbity is as old as the late sixteenth century, and once upon a time there was also just acerb. Acerbity is from the French acerbité, from the classical Latin acerbus, bitter. That’s from the Proto Italic akro-po-, with the ak- being from ak- (obviously).
 
Next is acrid, which makes sense being so similar to acid. It showed up in 1712, coming from the classical Latin acer, sharp, and you know that’s related to acerbic. It’s from the Proto Indo European akri-, which of course is from ak-. And there’s acetic, which makes sense considering vinegar has acetic acid in it. It showed up in 1808 from the French acétique, which means… acetic. Anyway, the word comes from the classical Latin acetum, vinegar, from the verb acere, to be bitter, from ak-.
 
Finally today, something slightly different, acrimony. It showed up in the mid sixteenth century meaning sharp or pungent in taste, then morphing to mean figurative bitterness in the early seventeenth century. It’s from the French acrimonie and classical Latin acrimonia, which both mean acrimony, from acer, and thus sharp. So because some things taste sharply, we now say people in a spat are acrimonious.
 
Sources
Online Etymology Dictionary
Google Translate
Omniglot
University of Texas at San Antonio’s page on Proto Indo European language