"The Qumran sect, the Gnostics, the Cerinthians, the Paulinists, the Jamesians, each had colored usage." That is why we have to be so aware when trying to understand what their meaning was, of course, their intended readership understood, or the Writer assumed they did ! hence they never felt the need to explain !
Also many words in the N.T take on a unique nuance of meaning, different to both Classical and Koine Greek.
"...became neutered and domesticated, stripped of sectarian meaning and catholicized." I presume you mean, PP, that the pseudepigraphical Epistles were written this way ? or are you pointing to a later Editing ?