Some researchers deem the name a loan word, possibly from a Pre-Greek language. Achilles' descent from the Nereid Thetis and a similarity of his name with those of river deities such as Acheron and Achelous have led to speculations about him being an old water divinity (see below Worship). Robert S. P. Beekes has suggested a Pre-Greek origin of the name, based among other things on the coexistence of "-λλ-" and "-λ-" in epic language, which may account for a palatalized phoneme /ly/ in the original language.