I don't know. I didn't put them in docs in the first place. They are mainly attachment s to emails i opened to look at in 'downloads' and then delete d from there. I don't use docs and was surprised to find when i happened to open it all sorts of stuff hiding there some of which i could delete (i hope) but some i couldn't. I suppose i could uninstall docs but i suspect google wouldn't let me do that. I sometimes feel there is someone else doing things to my phone when I'm asleep.
Open Google Drive on your phone, or go to drive.google.com on your computer browser, and see if there are a bunch of documents there that you might have saved (or might have been shared with you).
Presumably, they're only locally stored on your Nexus 5. Use a file manager app like Total Commander to see if you can find those document files, and delete them with the file manager.