Option-N and Option-P (What are they doing and how do I disable or rebind them?)
Thanks--the comments made me realize that I was barking up the wrong tree.
This shortcut was not a system shortcut but actually provided by Hammerspoon, specifically a feature (not a bug) of https://github.com/agzam/spacehammer, which is designed to provide convenient shortcuts for an &quot;Spacemacs&quot; workflow:

Other features

Alternative App Switcher Option n/p
Simple tab switcher for Chrome and iTerm Option j/k


Quitting the whole Hammerspoon process gave me back those keys.