I found this question, Is there a fix for the "Too many open files in system" error on OS X 10.7.1? , and specifically this answer
https://superuser.com/a/1180084/177312
and the output from that command was:
562 com.apple
580 firefox
716 eclipse
825 Microsoft
874 Google
950 plugin-co
953 plugin-co
1901 AppleSpel
2563 AppleSpel
2646 AppleSpel
WTF? Why does Spell waste all open files? I use it very, I think, averagely. A few documents in Pages, Safari and Messages. This is El Capitan 10.11.
How do I prevent the spelling service to grind my system to a halt?