In 16th c. daler, daller, a. LG. and early mod.Du. daler (mod.Du. daalder), = HG. taler, thaler, recorded by Alberus 1540, along with the full term Joachimstaler, lit. ‘(gulden) of Joachimsthal’ (in Bohemia), where they were coined in 1519, from a silver mine opened there in 1516 (Kluge). From LG. or HG. taken into other langs. In England before 1600 modified to dollar. (OED)