The stammering was, at this point, quite expected. The spell - or what he assumed was a spell, having picked up only enough Latin for incantations and the necessary botanical references - was not. He had no idea what quidvis meant, but Nott didn't seem to have a wand, so it probably didn't matter.
"I don't understand you." He ought to have left anyway; he knew the answer was yes. But as much insight as he could get into the man's thoughts would be welcome, really. "Does that mean you'd like me to go?"