We've discussed Valmay/Valmae before and got nowhere in particular; perhaps this might help. I know of a girl of 18, born in 1990 therefore, whose given name is Valmy. She is from an Afrikaans-speaking family, so the –y at the end is pronounced like the English –ay or –ae.
The V is Afrikaans is pronounced like an English F, and to get a V sound you must use a W; same as in German or Dutch. I don't know why her parents would have changed the final vowel to an Afrikaans spelling but left the first consonant; possibly because they intended her to be educated in English (she does attend an English-medium school) or because it looks closer to the English original that way.
Has anyone encountered anything like this in Dutch or German? Or got any sound idea when the name was first used?