Hi there! Welcome to the Community!
When you say mentions, where do you mean? Here on the Community boards, or on GitHub itself?
You could perhaps use the Community search function to look for posts mentioning specific keywords:
The menu UI only lets you choose one time limit (either before a certain date or after it) but you can enter the limit directly in the search box.
So for example, this search will find all posts mentioning Java in May:
java before:2020-06-01 after:2020-04-30
Unfortunately results are capped at 50, so a popular search term might be tricky to gather data for. You could search each category separately, perhaps, or use smaller time intervals.
If you’d like to make a feature request about the GitHub Support Community itself to make gathering this kind of data easier, please use our community feedback form.