Xebec

And, you know, pick a trivial example because grammar is so complicated.

The word Z-back is a great Scrabble word, X-E-B-E-C, and it's a three-masted schooner.

And the reason you two don't know that word is because A, it's not structured like other words in English, and B, there are no three-masted schooners.

And so because it's a special case in two ways that serves no function other than for Scrabble players, it's going to fade away.