Following The Grey Annals in volume XI of The History of Middle-earth.
2
The name Tumhalad is not explained, but it apparently incorporates tum, 'valley'. The name was at one point spelt with a hyphen as Tum-halad, which at least breaks the word down into its elements, though the meaning of halad is obscure. It may contain lad, 'plain', or possibly hal 'hidden'.