Úmarth meant 'Ill-fate'.

It was the name given by Túrin, for his father when he was taken to Nargothrond by Gwindor.

Túrin hoped that by denying his true name, and that of his father, that he might escape the cruel curse that Morgoth had placed upon his family. So he took for himself the name Agarwaen son of Úmarth, which meant 'Blood-stained' son of 'Ill-fate'.