In Lloyd Alexander’s Chronicles of Prydain series, one of the main characters is Gurgi, a sort of apelike wild man who Taran, the protagonist of the series, first encounters living in the forest. Though a pest at first, Gurgi later grows into his own as a hero and participant in Taran’s quest. Though Gurgi struck me as a Gollum equivalent at first the character has longer roots in English and European folklore of hairy wild people living in the forest, at one with nature… perhaps the pagan equivalent of The Noble Savage archetype.
Known as The Wild Men, or Wodewos, these creatures have mythic roots stretching back to the times of Gilgamesh. They became a popular artistic subject in Medieval times, appearing in paintings, woodcuts, and even costume pageants. Many assumed them to be real, drawing on travelers’ tales of apes and monkeys and Greek and Roman natural history accounts.
English folklore is full of other humanlike fairy, goblinoid, or animal creatures with colorful names like boggarts, shellycoats, and pyewackets. Other beings are singular, like Jenny Greenteeth or The Tiddymun.
If you want an original being of your own, check these out, all non-existent, but they could be.
English folk beings
Pugril and Wiggid