Nonplus

[A]ltering Vaudemont, to Vallemontanus, and metamorphoſing them, by ſuting them to the Græcian or Latin tongue, we know not what to make of them, and are often at a non-plus.

Being now made much abler to make their queries, of the ſecrets of that myſtery, by how much their often failings, had put them to often ſtops and nonpluſſes in the work.

And if both of them are at a perfect Non-plus, and Baffle to all Humane Underſtanding; is it poſſible for Natural Reaſon to comprehend what the Heart of Man cannot conceive?

I believe they'd ſoon be put to a non-plus—You'd be quite too much for them, I'm ſure.

You couldn’t have told it from my manner, but I was feeling more than a bit nonplussed. The spectacle before me was enough to nonplus anyone.