This is probably my favorite version of pony humanization. Of course, fully humanized ponies are fun, but it kind of takes away their uniqueness. And the "Ponies but with hands and feet" version is pure Uncanny Valley for me really.
The name comes from Silenus, an old man with the ears, legs, and tail of a horse who was a follower of Dionysus (Greek God of wine, debauchery, theatre, and madness). The term "sileni" is used to refer to satyr-like creatures that had the features of a horse instead of a goat.