In Domesday Book this is mentioned as one of those given by William
the Conqueror to Robert Earl of Morton, when he made him Earl of
Cornwall. In the extent of Cornish acres 12 Edw. I. it is valued in
eighteen.
[This manor, which has given name to the parish, has drawn its own
from Trev Alga, the noble house; Alga (I.) signifying noble, as in
Inis Alga, an old name for Ireland; and this affords one instance more
of the necessity of recurring to the kindred dialects of the British
in explaining Cornish names. W.]