LotR orcs are corrupted elves as well.
Even that isn't totally cut and dried, it's almost as confusing as TES lore.
Quote :
" Orc origins in Middle-Earth cosmology are described in The Silmarillion. Morgoth, a
powerful, self-serving Vala (god-equivalent) fallen into evil, captured some Elves
(Quendi) early in the existence of their race.
“Yet this is held true by the wise of Eress?a, that all those of the Quendi who came into
the hands of Melkor [later Morgoth]…by slow arts of cruelty were corrupted and enslaved;
and thus did Melkor breed the race of the orcs, in envy and mockery of the Elves, of whom
they were afterwards the bitterest foes.”x
This idea is tidy and strongly appealing with its parallel of beautiful elves directly
linked to ugly orcs. Nonetheless, in his own varied writing about orcs, Tolkien
vacillated between this concept of orcs-from-elves and a related concept of orcs-
from-men.xi He even toyed with the idea that orcs were cunning animals, lacking
the spiritual element of sapient beings, or with the concept that orcs were Maiar
(divine spirits) serving Morgoth who had been corrupted into orc-form. Both the
orcs-from-men and orcs-as-beasts concepts seem to come from Tolkien’s personal
reluctance to taint elves, his “ideal” race. However, he kept being drawn back to
the idea of orcs-from-elves in multiple drafts of his own orc essay, written through
1959 and 1960, and he acknowledges that orcs-from-elves was the most workable
origin for the Middle-Earth timeline he desired. xii
Christopher Tolkien, editing The Silmarillion after J.R.R. Tolkien’s death, opted for
the orcs-from-elves origin. "