READER QUESTION: When did the Rabbis start prohibiting the use of “The NAME?”
It seems not possible to discover an exact time/period when the rabbis prohibited the uttering or writing of "The NAME", the Tetragrammaton. But it seems to have originated during the Second Temple period, in the 5th century BCE.
It is recorded in the Mishnah (which itself was not compiled and written down till the 3rd century CE and later) which explains that the sacred name was restricted only to the Temple, and even then only on specific occasions. Thus, outside the rabbinic circles, the pronunciation of the sacred name was already not permitted.
Then, in 70 CE, when the Second Temple was destroyed, even the rabbis had no authorized place to speak the sacred name, and it fell into complete disuse. The consequence is that the pronunciation was lost, leading to today, where we spend a lot of time arguing with each other about the proper pronunciation.
Oddly enough, rabbis recognize that there is no prohibition of speaking or writing the sacred name, yet they cling to the old tradition.