The tune to this carol is Greensleves. Rumor has it that Henry VIII wrote the song for Anne Boleyn - but, it is only rumor. We do know it
was around in Elizabethan times since Shakespeare mentions it by name in his play The Merry Wives of Windsor. It is played while traitors are hanged. (Charming!)
In 1865 William Chatterton Dix wrote The Manger Throne. Three verses of this poem became What Child is This?