Rabbins and rabbis

In my research for this blog I noticed something that I hadn't previously known: in English the prevalent tendency, by far, was to write "rabbins" as plural for "rabbi" up to, and including, well on into the 19th century.

Why is that? I knew that in German a rabbi is a rabbiner. English is Germanic &c. But that hardly seems a satisfactory explanation. Given that, when did rabbins become rabbis? And why?

The handy dandy Babelfish translator tells us that a rabbi in certain other languages is:

rabijn in Dutch
rabbin in French (aha!)
rabbiner in German
ραβίνος (rabinos) in Greek
rabbino in Italian
равин (rabin) (in Russian
rabino in Spanish
rabinus in Latin
ラビ in Japanese (sorry, I get lost here!)

And, of course, רב rav in Hebrew. Presumably every other language got its "rabbi" from references in the Christian scriptures, like Matthew 23. And the original language of said scriptures was Greek. In Greek the instances of "rabbi" were written as ραββι which can be written neatly in English as rabbi. Presumably the Hebrew word the writers of the Christian scriptures had in mind was not רב but רבי rabbee (י"א ribbee).

But what are rabbins in English?

Comes the Oxford English Dictionary to shed a little light:

rabbin The source of the n in th[is] forms is obscure: it may have originated in pl. forms (rabbins, rabbini) on the supposition that the pl. of the Heb. word was *rabbin (cf. assassin, bedouin, etc.).]

Aha! But we had a secret: the word they were looking for was rabbeim or rabbanim.

One more OED "fact":

to designate the chief Jewish authorities on matters of law and doctrine, the most important of whom flourished between the second and thirteenth centuries of the Christian era

It's nice to know that the OED decided how rabbis are ranked!