Dear R’ Michoel, With your indulgence, I’ve broken up your question into several parts. Caveat: I’m writing this quickly and there are some ideas contained here there not completely developed, not to say half-baked (such as the connections to other תק words such as שתק and בתק)..
QUESTION: I was wondering about the leprous sore called “נתק” – The bilateral string תק seems to be associated with being held firmly in place, except in verb נתק, it means precisely the opposite, i.e. removed or plucked out etc. Perhaps like verb לשרש, to “uproot,” even though שרש means root. I recall Rabbi Jeremy Steinberg cited numerous examples of this phenomenon in the past. So regarding the leprous נתק, does it etymologically mean “removed” or “plucked out”, i.e. that the hair is removed from that sore on the head/beard? Or is it from general meaning of תק, firm and lasting, since that type of sore lasts longer than regular נגעים since it’s on the head? -Michoel Green