As I wrote in OP, I used to have this theme/component earlier, but no longer.
So I can’t trace it in either theme or components.
@merefield the topic mentioned by you was closed after the OP found that updating the site solved the issue. But in my case updating the site thru one-click and thru rebuilding, didn’t help.
One thing that has just come to my mind, after @Heliosurge 's post, is that I should re-install the same component afresh, and then check. May be 
it’d go away.
Will report.