Steuer is the word Austrians type when they look for anything related to tax, and Bitcoin is used unchanged in everyday German. The compound bitcoinsteuer is therefore exactly what a searching user has in mind: how is Bitcoin taxed, and who can help? Tax rules differ between Germany, Austria and Switzerland, so a country ending matters more here than for most topics. The .at address tells the reader that the content and the service follow Austrian rules.
The name belongs to the Tax category and the Bitcoin Tax & Law DACH set, next to the Austrian and Swiss Steuerberater and Steuerberatung names in the portfolio. It suits an Austrian tax practice with a crypto focus, a software tool that calculates and documents Bitcoin gains for Austrian returns, or a publisher explaining the rules to private investors. Short and descriptive, it also works well in advertising and on printed material.