I always assumed that the chorus phrase was Malayan but the verses were translations and add-ons.

Yes, that's what I'm also assuming. But how would Burke translate? one wonders.

"Malayan" could refer to several different subjects, I suppose.

If Burke mentions it 4 times and calls it "Malayan," it seems odd there wouldn't be *some* kind of connection. Exoticizing I can understand, but why not just call it a "chanty" the other times? Why emphasize "Malayan" here, for instance?:

Pg252
Love, says an old Malayan chanty which I learned at West India Dock—Love is kind to the least of men. God will it so!

It seems to have become Burke's pet reference. Perhaps he was so struck by it that he asked someone the meaning when he heard it, and rendered it in his literary way.