Language Of Confusion: Tense, Part III

Even more words descended from the Proto Indo European root ten-, to stretch. Today these words… well, they’re quite a stretch.
 
Tone for example is not something you’d think was related to tense. It showed up in the mid fourteenth century meaning a musical sound, then a manner of speaking in the seventeenth century and shortly after the “firmness of body”. It comes from the Old French ton and classical Latin tonus, just tone, and before that the Greek tonos, also tone (and tuna fish, which is certainly related). And yeah, tune is from the same place, literally called an “unexplained variant” of tone. A tone is a sound, though, while a tune is a bunch of tones.
 
There are also a few variants, like baritone, which showed up in the seventeenth century from the Italian baritono, from the Greek barytonos. Barys translates to heavy or deep, so with tonos, a baritone is a deep tone.
 
Then there’s tonic—yes, like a potion or medicine. When it first showed up in the mid seventeenth century, it actually meant relating to muscle tension, meaning it’s the first one of these words to make sense as being related to tense. By the end of the century it started to mean relating to healthy muscles, then in the mid eighteenth century shifted to mean something that restores to health. It comes from the Greek word tonikos, tonic, which is from tone, which is from ten-. Still no explanation as to how a tone relates to stretching, but there you go.
 
There are a few variants on that, too. Isotonic is relatively recent, having shown up in 1776 (there’s actually a section of my grocery store labeled isotonics in spite of Microsoft telling me that’s not a word). It’s also from Greek, isotonos, with the prefix meaning equal or identical. An isotonic is an identical tone. Plus there’s catatonic, which showed up in 1899 (catatonia having shown up in 1888). It’s from the Latin catanoia, with the cata- prefix coming from the Greek kata, against, and meaning down in this case. Catatonia is… to tone down???
 
Sources
Online Etymology Dictionary
Google Translate
Omniglot
University of Texas at Austin Linguistic Research Center
University of Texas at San Antonio’s page on Proto Indo European language