British composer Peter Warlock (b. Phillip Heseltine, 1894-1930) wrote this charming little lullaby as a Christmas carol in 1926. (You can hear the original here, in an arrangement by Andrew Carter.)
I've re-written the lyrics slightly—certainly it could still be sung as a Yule carol—to make it into a general, any-time lullaby for any boy-child: baby god, baby warlock, or otherwise.
For this I make no apologies. I suspect that a man who, because of his active interests in the occult, took the name "Warlock," would be delighted to know that witches were singing his song to their babies.
Absolutely delighted.