I didn't think I had been confusing. If you look above, I never said mensure had been used to describe the entire string length. Instead, I clearly and consistently said "nut to bridge." Is that understandable?
And no, I do not seek any "ur-usage." Instead, I would imagine you - or anyone else - could identify one of those many "random sources [you] have read" which "all" use the term differently from what I have been able to identify, and from what my wife was taught in violin-making school.
I acknowledge the possibility that the multiple pretty well-respected sources I quoted and the instructors at my wife's school might be mistaken. If they are, it should be possible to cite something other than one's personal understanding or recollection. My wife and I have not conducted an exhaustive review of her entire library, but we did not identify any source defining the term as you do.
I recognize that this is a ridiculously minor point, and I do not intend to insult or offend anyone, and I probably should not continue this discussion which many/most likely consider unimportant.