Etymon has no etymon, fittingly enough. It existed only in Greek, with the generally accepted meaning of a true word, the original word, the source of all related words to come later. But it is hard to be sure about this. How could a word like etymon appear out of nowhere and suddenly install itself in ancient Greek, out of the blue, so to say. It is also strange that there seem to be no descendant words based on etymon, apart from the obvious immediate derivatives: etymology, etymologist, etymologize. All this would make etymon unique, unprecedented. The OED suggests a possible way to bypass the puzzle. The philologist Brugmann, a century ago, proposed an origin for etymon in Old Aryan, s-etumos, with the suffix s derived from IE (Indo-European) es, meaning it is, it is true. If this were correct, it would not only provide etymon with proper ancestors but would also assure a huge number of cousins.
Es is one of the most prolific of all IE roots in the language. At the outset, it had the meaning to be, extending as es-mi in Germanic and eam in Old English to modern am; and from es-ti to German ist to French est to English is. It turned up again in Old English sie, meaning it is so, si in romance languages, and our word yes. And again it moved as sont to soth in Old English, and to sooth (forsooth) and soothe.
The connection of soothe to yes is strange but true; it takes a bit of relaxing to get it straight in the mind. I suppose that if something is, and is true, and leads to nodding of the head, and brings the archaic response sooth, or the modern answer yes, it is a soothing experience. The truth is not always soothing, but in a better world it ought to be.
- Lewis Thomas: Notes of A Word-Watcher (1990)
