Why does a find field value in one application show up in a the find field of another application?
I've found it. It's called FindScrap. 

At the command line, enter:

defaults write &lt;program&gt; FindDialog_UsesFindScrap -bool NO


Where &lt;program&gt; is something like com.barebones.bbedit.

(source: https://www.barebones.com/support/bbedit/ExpertPreferences.html#texts, accessed 20180203)