The whole 'don't say his name!' business

I'm wondering, where exactly does this come from?

In my own readings, I've only encountered mention of this in one other
novel -- Vernor Vinge's SF/fantasy tale "True Names" -- where the author
talks about how knowledge of any wizard's real name automatically gives
one power over him.

For her stories, Rowling undoubtedly must've drawn upon the same
historical legends and body of lore that Vinge did. But which ones? Greek?
Arthurian? Dunno.
.

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