A graphical object composited just in time in display scanning process.
(Or in other words, a graphical object on screen that is not present in a framebuffer of any kind.)
This is immediately what popped into my head, and I clicked the link thinking it was going to be some old-school game dev content.
There was a time before 8bit video games.
https://www.merriam-webster.com/dictionary/sprite
I personally associate the term Shakespeare's The Tempest: https://en.wikipedia.org/wiki/Ariel_(The_Tempest)