[ianleighton]

Tisane probably comes from French, where it is relatively common (at least understood, and a stickler for tea would correct your usage) and perhaps one would use it in English like other French culinary terms like “à la mode”

[klipt]

Wiktionary says it went

English <- French <- Latin <- Greek

https://en.wiktionary.org/wiki/tisane#Etymology

Interesting that in English it starts with the "tea" sound, but has a completely separate origin (I don't think the ancient Greeks were even aware of Chinese tea...)