Henri Beyle, the famous French writer, chose Stendhal as his penname with a French pronunciation and not a German one.
Contrary to popular belief, the writer did not borrow his pseudonym from Stendal, the German city where a famous archaeologist was born (Johann Joachim Winckelmann).
According to some Stendhal scholars, his name is the anagram of Shetland, the Scottish islands very much loved by the French author.
We still do not know why he picked his own pseudonym and, apparently, Stendhal himself didn’t know how to pronounce it properly. That’s why the French pronunciation has prevailed in the long run.