Analyzing frequency of co-occurrence

I am working on some qualitative analysis of post-secondary course offerings in a nationwide scan. I have a spreadsheet listing a large number of courses in an academic discipline. In one of my columns, I've listed three or four themes or keywords relevant to the course. I've already used unpivot in Power Query to put each theme on its own line, and then used a pivot table from this to calculate how often each theme occurs. But I'm having trouble taking my analysis to the next level.

I want to analyze how often themes occur together. For example, how often does the theme "business acumen" appear on the same line as "venture capital". Which themes never appear together? The courses included in my scan all have unique identifiers so I'm hoping this will help.

I'd really like to be able to visualize the co-occurrence of themes, but I'm not sure where to start. I am having trouble Googling solutions because I'm not sure what vocabulary to use.