Heuer is a surname that comes from the German word "Heu" meaning "hay." The name is occupational in origin, especially so, when it serves as an element in a compound. Heumaier would refer to the officer who oversaw the delivery of the hay harvest. Heuwemenger is the equivalent of "Heuhändler" meaning hay merchant. The surname Heuer was first found in what are now Germany and Switzerland, where the earliest mentions of the name include Cunrat der Hewer in Württemberg in 1329, Heu in Konstanz, Hauwemenger in Frankfurt in 1387, and Heurechen in Zürich in 1400.
https://en.wikipedia.org/wiki/Heuer