Creatures from the dark forests in the south of Middle-earth. Though they seem to have been unknown in the northern lands, the Orcs used their name as a favourite form of insult.
Notes
1
Apes are only vaguely stated to live in the South, but this presumably refers to the southern parts of Far Harad (Harad simply means 'the South'). This implies that, beyond the desert lands of the known parts of the Harad lay greener areas covered in swathes of forest or jungle.
2
The use of the term 'ape' is only very approximately used as a simile, and so it is hard to narrow down exactly what kind of ape is intended. There are numerous possibilites, and indeed it is conceivable that the word is used in its older, broader sense to mean an ape-like creature or monkey of any kind.