Fist solution : hire a developer to add this feature to your certificate module. I don't recommend this solution because several files would have to be modified : the form used when you create a new certificate instance to add a select menu to choose the activity (SCORM video for instance) to use, the database to store this information, the certificate itself to print the activity's name. Quite a lot of modifications in fact and quite complicated. Additionally this would complicate a lot future upgrades.
Second solution: use a simple workaround, why no use the custom text field available in each certificate for the activity's name ? Of course it would not be automatic and you would have to copy yourself the name of the activity in that field when you create the certificatte instance but it would require no modification to the certificate module
third solution : abandon the certificate module and use Mark Nelson new customcert module where his feature is included (you need to add a "gradeitemname" element to your customcert. The only drawbacks of this solution is that this module is no yet released so you would have to download it here https://github.com/markn86/moodle-mod_customcert (choose the branch according to your moodle version) and hat thee is no documentation available on this new module so you would have to figure how to use it (or ask quesions here)
I am using it on a production website and I am very satisfied of the results so far.
I hope Mark will be able to do a proper release in a not too far future