Younger son of Beregond in Tolkien’s aborted sequel to The Lord of the Rings: The New Shadow (PM/411). It may have the same etymology as earlier (unrelated) N. Borlas (Ety/BOR).
Sindarin
Borlas
noun. lasting, faithful joy (male name)
borlas
masculine name. Borlas
bór (“faithful, enduring”) + glass (“joy”)