Thanks for this, Charlie!
I was going with the assumption that foreign rules of grammar need not apply to words that are imported into English. Here's a passage from the King James Bible:
"Above it stood the seraphims: each one had six wings; with twain he covered his face, and with twain he covered his feet, and with twain he did fly." (Isaiah 6:2, KJV)
But I think your comment is just as correct. ✌