Clearly, arbata comes from the same herbal tea origin, just the h got dropped somewhere along the way, herb -> arba, tea -> ta

This would appear to be confirmed based on regional dialects from this area.

In the Samogitian dialect of Lithuanian it's spelled "erbata", however the first "a" in modern Lithuanian isn't stressed, so it's very similar. Also in Kashubian (spoken in parts of northern Poland, often considered a dialect of Pomeranian) it is the same as modern Lithuanian.

On the other hand in Sambian Prussian it is "tejs", which is similar to "teja" in modern Lativan. It's interesting how two different forms emerged in the same geographic area.