Further tangent: at least part of it has been "die Tschechei" in German since 1918 per the Wiktionary[0] and that's certainly the word people used in West Germany in the 80's, and I believe it's used widely today despite "Tschechien" being official[1].
The Wikipedia article (in German) suggests Tschechei is from Čechy which seems to be Czech for Bohemia. But I am not Czech nor Cseh nor tschechisch nor Čech so I may soon stand corrected. :-)
[0]: https://de.wiktionary.org/wiki/Tschechei [1]: https://de.wikipedia.org/wiki/Tschechien
So if you hear someone using a country name you've never heard before, I can understand being cautious about adopting it :)
[1] https://en.wikipedia.org/wiki/Alternative_names_for_Northern...
And if you obviously have no clue what you're doing and don't even try to buy a drink, they'll definitely know you aren't a cop and offer you the weed.
I think it's quite a misconception about Czechia being super weed friendly. As a tourist you are most probably going to get scammed on streets of Prague. If you want to feel more free about weed consumption Netherlands is the place to go to.