“thaler” is just a big silver coin. The first big silver coins issued in Europe since Roman times were struck at Joachimsthal, in Bohemia, around 1474. “Joachimsthaler” got abbreviated to “thaler”. The big coins were found to be very useful, and “thalers” ended up being struck all over Europe, on a whole range of different weight-standards.
And let’s not forget the silver Maria Theresia Thaler of 1780, which was such a big hit in the Middle East that the Austrians have been minting it, substantially unchanged, ever since, and which was the unofficial (and in some cases near-official) currency of much of the Arab world for centuries