Did the られる potential form come from 得る?

Question

One of the shows I've been watching lately kept using some more classical forms of Japanese for style purposes, that I was not too familiar with ; this led me to notice how 得る{える} was often used as an auxiliary verb. For example, this makes constructions like 有り{あり}得ない{えない} way easier to remember now that I can see the how it's built.

Looking more into it, it seems (explained in here) that it can indeed be used to indicate potential as a somewhat old/formal form.

The modern potential form 〜られる/〜える looks very similar however (as alluded to in here), especially for godan verbs.

My hypothesis is that the modern 〜える (for godan verbs) directly comes from 得る, and that 〜られる (for ichidan verbs) was initially some kind of alternate construction (the only thing that comes to mind is a contraction of something involving ある like 食べれ・あれ・得る → 食べられる).

Is there any definite proof of the connection between the two? What transformations led to the construction of the modern form, if there is such a connection?

Answer 1

According to this paper, the current Japanese 可能形 at least in part likely derives from the passive, due to, as stated in the paper, the passive expressing:

主体の意志とは関係なく動作が実現してしまう（こと）
An action realized without regard for the will of the subject

A cursory search on wikipedia suggests that the passive る and らる endings (which developed into the current れる and られる endings) derive not from 得る but 生【あ】る, with る attached to the 未然形 of verbs that undergo 四段活用, ナ変格活用, and ラ行変格活用 (e.g. 住む→住まる) to preserve the original ある pronunciation of the suffix, and らる attached to the 未然形 of all other verbs (e.g. 当つ→当てらる) as their 未然形 wouldn't end in a member of the ア段. While this does not explain why ら was selected for らる, it does confirm that the られる ending most likely does not have anything to do with 得る.

EDIT:

As an aside, the trend where old 二段動詞 became 一段動詞 (上ぐ→上げる、寝【ぬ】→寝る、生く→生きる/生ける、〜る→〜れる、〜らる→〜られる等) is loosely referred to as 二段動詞の一段化 (you can read a bit about it here and here), and has absolutely nothing to do with 得る.