The surname of GEISZLER was a Swiss and German surname of two-fold origin. It was an occupational name for 'one who looked after the goatherd, the man who tended the goats'. Occupational surnames originally denoted the actual occupation followed by the individual. At what period they became hereditary is a difficult problem. Many of the occupation names were descriptive and could be varied. In the Middle Ages, at least among the Christian population, people did not usually pursue specialized occupations exclusively to the extent that we do today, and they would, in fact, turn their hand to any form of work that needed to be done, particularly in a large house or mansion, or on farms and smallholdings. In early documents, surnames often refer to the actual holder of an office, whether the church or state. It was also a locational name for someone who lived in a house marked by the sign of the Holy Spirit (normally depicted as a dove), and the name also occurs in Germany in the mid-14th century. The name is also spelt GEISS, GEISEL, GEISEN, GEISINGER and GEISSLER. Local names usually denoted where a man held his land, and indicated where he actually lived. Almost every city, town or village existing in the Middle Ages has served to name one or more families. Where a man lived was his means of identification. When a man left his birthplace or village where he had been known, and went elsewhere, people would likely refer to him by the name of his former residence or birthplace, or by the name of the land which he owned. A notable member of the name was Heinrich GEISSLER (1814-79) the German inventor, born in Saxony. He became a glass-blower and settled in Bonn in 1854. The GEISSLER tube, by which the passage of electricity through rarefied gases can be seen, and the GEISSLER mercury pump are among his inventions. Because of the close relationship between the English and German languages, some Germans are able to transform their names to the English form just by dropping a single letter. Many Germans have re-spelt their names in America. After the start of the first World War, Germans in great numbers Anglicized their names in an effort to remove all doubt as to their patriotism. Afterwards some changed back, and then during World War II the problem became acute once more, and the changing started all over again, although not with as much intensity. Many immigrants from Germany settled in Pennsylvania.