The language files may be fine, but the other templates and override files that should be echoing that information could be changed to not display that ...
If you were to have a clean copy of Zen Cart v138 and put that on the left and then the copy of your site on the right you could do a compare of the files to see what is different ...
In your case, you need to compare templates ...
I open the left side to:
/includes/templates/template_default/templates
and then on the right side compare that to:
/includes/templates/your_template_dir
and see if you can find the differences ...
You can also do this with:
/includes/modules
/includes/modules/your_template_dir
and any other templates and override directories ...
You also said you found the text define for:
discount savings
so, you can search for the constant for that (it's in CAPS) to see where it is used in the original files and where it is either missing or commented out in your templates and overrides files ...