I have updated the extcal module. The latest version allows to use the calendar name in the output for each entry. If you have several calendars about different topics, that's an elegant way to indicate the appropriate topic for each entry.
Version 1.2.0 is attached to this post.
here the recent changes:
* 1.2.0 2018-06-14 - added place holder for the calendar name
* 1.1.11 2018-06-13 - updated help pages
* 1.1.10 2018-06-12 - updated sabre-dav to 2.1.12
* 1.1.9 2018-04-12 - correct the behavior for including module css
PS: Thanks to HP for suggesting the new feature