Fixing one error log. PHP Warning: constant(): Couldn't find constant BOX_HEADING

Each time I access our admin, it throws up an error in the logs:
PHP Warning: constant(): Couldn't find constant BOX_HEADING_MINE in /home/..../admin/includes/functions/admin_access.php on line 854

I would like to trace the old unused module that comes from.
May have been a mod like Admin Profiles or something but I don't recall.
Only the box_heading_MINE gives away that I had tried to install and edit at some stage. (I would have called it 'mine')

Any ideas how to use this error message to trace back and remove the files, to stop the logs?
Thanks

In admin, there is a tool called developer tool kit.

In the lower left corner if you enter the define value (all caps as presented) and select the case sensitive block, then search at least the admin side, reference to where the define is used should be provided. From there you can search down further for the problem file(s).

Hi, yes I'd tried finding a reference using dev tools, but came up empty.
Then I just realised the files may be all gone, but database may have something still.
Found it under Admin Menus table and deleted the customer entry. (Hope that was ok to do, but I backup up database)
Hopefully that's the fix. Were 1000s of error logs because of it lately.
Thanks.
I'm actually trying to tidy up a bit ready for your assistance mc123 :-)