Recalling an earlier discussion of this word I wonder whether there are other English words with the peculiar ending -ae.

Antennae

There are a fair number of Latin-derived plurals (like antennae, as HZ7N mentions) and genitives (arbor vitae).  There are Scottish dialect words, like “brae” and “nae”.  There are a few obscure loanwords from Maori and other Polynesian languages (e.g. “kanae”, a kind of mullet fish, “marae” and “malae”, loanwords from Maori and Samoan, respectively, for open spaces or courtyards), used mostly in New Zealand and that area. There’s “min dae”, South African Army slang for the last few days of one’s military service.

The only other common one that doesn’t fall into any of the above categories seems to be “reggae”.

edit: corrected reversed attribution of “marae” and “malae”, thanks to nudge from Jory Dayne

This may count as cheating, but if you enter *ae at Onelook, you’ll get a whole lot of hits.

And about that ‘min dae’. I have reason to believe that that ‘dae’ is from ‘dage(n)’ (days), so I wonder if it really counts. Eliza?

Edit: that link seems to bring up a search on “ae” and not “*ae” although the asterisk appears in the link. Okay, I guess you’ll have to add that * yourself. And of course most of these words fall into the categories as indicated by Dr. Techie

The OED and various online sources I checked indicate that the Afrikaans plural of dag is dae.  One of the ways it differs from Dutch, I suppose.  I’d say that a better argument that “min dae” doesn’t “really count” would be that it’s a regionalism of pretty limited distribution, not something one could use in an English text without explanation and expect to be understood outside of South Africa.

That’s what I meant to say (more or less). Whether it counts or not we can leave to Senning.

How unsatisfactory it is that there is no clear knowledge about the origin of this fairly recent word.