The usual sources only say that "Stöpsel" was from "Low German", akin to "stop". I was wondering about the suffix.
The question arose wondering whether En "stop" is cognate, but it is interesting to me because of the several alternatives I have in mind:
The word is a doublette of "Stopfen", in which the f seems to be from the second consonant shift, in which Low German "Appel" did not participate; The s is probably not from f. Alas, I have no older material at hand to compare, and so, as the Original root is linked to PIE *stew- (cp e.g. "Stau") I wonder whether labial w was completely lost. A Stopfen is also something woven to fix holes in clothes, hence Stoff "textile" seems close.
- That is a very unlikely avenue, in my book. w did not regularly fricate, nor was it subject to metathesis (wp > pw?), nor did f regularly become f in any case, that I know of.
-l also appears like a diminutive suffix, e.g. in "Madl" (Mädchen, Magd), "Bübele", that is popular in Bavarian, in Yiddish, but perhaps also Saxon, or anywhere.
- This does not explain the s. I wonder also whether stub, stubbble, Stumpf, Stoppel belong here or below:
-l alpears as instrumental suffix in needle, paddle, and involved *-th, thus its deemed an explanation of the illusive *threshold. German s and z are allophone in Ablaut due to Auslautverhärtung, and z generally corresponds to *t (Zahn ~ tooth). pt is generally not phonemic in German, but cp eg "Klapptisch".
- Nothing fits together in this one. The documentation in wiktionary isn't great ([[threshold]] still shows a redlink for the suffix), and my memory is even worse.
Since this is all very messy, I'd appreciate anyone who can give me a clearer picture.