Actually I'm not sure you want to get into the etymology of "Tea".
We will be here a while and I have a whole rant in there about "Thailand" that no one needs to read.
Yet everyone calls it tea, it's sold as tea as well. First time I'm hearing the term infusion actually. Tea is just hot water with added flavouring and that's how the word is used.
Funnily enough I have dried orange peel pieces to make tea out of as well.