The Names of Sauron

[Pitchwife]

Originally Posted by Legate of Amon Lanc

It would be also interesting to know what was Sauron's name "in the beginning" (as Aulë's Maia), but that we might possibly never learn...

Actually, we do know: according to a paper by Tolkien from the 1950s/60s,

Sauron’s original name was Mairon, but this was altered after he was suborned by Melkor. But he continued to call himself Mairon the Admirable, or Tar-mairon ‘King Excellent’, until after the downfall of Númenor.*

(quoted by Helge Fauskanger in this article on Ardalambion, which also discusses the changing etymologies for the name Sauron, none of them very flattering).
Then, of course, we have the name Annatar, "Lord of Gifts" (or, according to a later source, Aulendil) which Sauron used as an alias in his dealings with the Gwaith-i-Mirdain (and possibly the Númenoreans as well?).
All this makes the use of Sauron's 'right name' by his subordinates all the more puzzling. The need for clarity in diplomatic negotiations sounds like a good explanation to me, but I'd like to hear some other opinions.

*Afterthought: After the fall of Númenor, Sauron

was unable ever again to assume a form that seemed fair to men, but became black and hideous, and his power thereafter was through terror alone.

(LotR Appendix A) - so maybe even He himself decided he couldn't get away with using his former name anymore.