The standard advice in Silicon valley is, "if you've ever touched it, put it on your resume." This advice does not come from flakes but from serious, professional people.
What if they ask?
Then you tell them that you really got into COBOL with your best friend fiffteen years ago, and it was kind of fun. You're pretty sure you could reconstitute it in a couple of weeks. After all, it's just another programming language.
If you're talking to a manager who doesn't know COBOL from a hole in the ground, it won't matter. The only thing the manager is responsible for is going down a check list: the position requires knowledge of COBOL; applicant has knowledge of COBOL. Check.
If you're talking to a COBOL engineers, you say "I've played with it a bit a long time ago. I'm sure I could get it back with a couple of weeks of hard study It's a fun dinosaur."
After all, you're not applying for a job as a COBOL programmer, functional literacy is what you need and your research skills are tops. So, don't worry.
And, when you get a job, don't kill yourself. The first six months are always hard. After that, what you must do is figure out how to minimize the amount of work you're doing (for the corp) so that you have time and energy to do the work that needs doing ( for the world)
Joanna