It's been almost 10 years since I wrote the post above and I just wanted to make a few corrections and clarifications:
1. The earliest hamlet is now spelled Guggemoos on maps, not Guggemos. You can see it on Google Maps here:
http://goo.gl/maps/nJtvV 2. I erroneously said that the hamlet was near the border with Switzerland; this is wrong. It's near Austria.
3. I have more to say about the meaning of the first part of the name, "Guggi". In Dr. Guggemos' history (see
http://home.allgaeu.org/aguggem/ahnenf.htm ), he told a story in which, sometime around the 11th century, an Alemmanic tribesman named Gugo settled on the edge of a marsh. Dr. Guggemos believed that this man's land became named after him as "Gugo-am-Moos," and that all Guggemoses therefore descend from this progenitor. In the words of Dr. Guggemos:
Als Träger des Namers habe ich lange und viel darüber nachgedacht und auch eine Lösung gefunden, die ich als die allein richtige ansehe. Zu Beginn der 2. großen Rodungszeit, also wohl im 11. Jahrh. kam ein Alemanne mit dem Namen Gugo oder Gogo auf der Suche nach einer günstigen Niederlassungsmöglichkeit mit seiner Famile in die Gegend, wo heute der Ort Guggemos liegt. Es gefiel ihm dort auf dem hochgelegenen Platz mit der schönen Fernsicht und der Sonnenbestrahlung während des ganzen Tages. Er errichtete sich hier am Rande eines sicher nicht sehr aus gedehnten Mooses ein Haus für seine Familie und begann den Wald zu roden zur Gewinnung von Siedlungsland für einen landwirtschaftlichen Betrieb. Die in der Umgebung bereits lebenden Alemannen nannten ihn den Gugo am Moos, Woraus mit der Zeit Guggemos wurde. Der Siedlung, die er geschaffen hatte, gaben sie den Namen Guggemos, benannten sie also nach dem Siedler und der Lage seiner Siedlung. Der Namen Gugo scheint unter den Alemannen in unserer Gegend verhältnismäßg selten gewesen sein. Er ist die Kurzform eines ahd. FN, etwa Guggenhart, Gugginhart, Guggenbert oä.
This interpretation is based on fairly slender evidence, though. He bases his argument on the fact that "Guggemos" is a place name that only arose once, and so he argues, it was more likely to have come from a personal name rather than from a feature of the local landscape. I do not think there is any surviving evidence of a "Gugo" having existed, though -- his existence in the 11th century is speculative. Dr. Guggemos also admits that the name "Gugo" was not a common one.
The earliest linguistic evidence that Dr. Guggemos turned up points to two early spellings of the name in the 1300s: Guggimos and Guggemos. Guggemos is the one that has propogated most widely today, with Guggenmos probably being a variant that stemmed from this name slightly later. The earliest recording of the name as "Guggemos" was made by a clerk in Augsburg in 1366, regarding an inhabitant of the town of Mittelberg. The form of the name "Guggemos" might point to an original meaning of the name as "Cuckoo-Marsh" (after the local pronunciation of the word for cuckoo) or "Berry-Marsh" (after a local word for a certain type of berry), or perhaps "Gugo's Marsh", as Dr. Guggemos believed. This interpretation would assume that the earlier pronunciation of the name Guggemos was either Gugo-mos, Gugu-mos or Kuku-mos; the unaccented "o" or "u"syllable would have softened to an "e" during the vowel shifts that occured as Old/Middle High German evolved into Modern High German.
The earliest recording of the name as "Guggimos" was 6 years later than the recording of "Guggemos." Dr. Guggemos thought that "Guggimos" was just an arbitrary spelling error by a clerk, but my mother (who is a professional translator with an advanced degree in German) disagrees. The 1372 recording of "Guggimos" came from the sale of a farm by a "Benz Guggimos," on the site of the current hamlet of Guggemoos. This recording therefore came from a farmer who lived on the original plot of land from which all other forms of the name descended. We might reasonably assume that a farmer from the original family plot would have supplied a pronunciation that was more archaic than one supplied by a town-dweller some distance away. The vowel shift from Old/Middle High German to Modern German, which is mentioned above, occured in towns first. Town-dwellers like those in Augsburg would have stopped pronouncing the "i" first, while people in outlying farms would have kept pronouncing it for while longer. Even though it was recorded slightly later than the first spelling as "Guggemos", the 1372 document therefore may be recording the earlier pronunciation, coming from before the vowel shift occurred.
If "Guggimos" is the more archaic form, then it is unlikely that the original meaning of the name was Cucko-Marsh, Berry-Marsh or Gugo's Marsh. This is because vowels did not shift from o/u to i. They instead softened from o/u/i to e (See "An Introduction to the Historical Study of New High German,"
http://tiny.cc/qf07ow ). If we accept that "Guggi" is the older form, then we can refer to what Dr. Guggemos said about its meaning: "Einige weitere Namensforscher leiten das BW Guggi von der kleinen, vor allem in Hochmooren hausenden Sumpfkröte Guggi her, die einen kuckuckartigen Ruf ausstößt, dem sie ihren Namen verdankt." Thus a "small marsh toad," locally called a "Guggi" after the cuckoo-like call that it gives, might be what gave our family name its stem.
I think one can understand why we would be more attracted towards a meaning of our family name as "Alemmanic Tribesman Gugo's Marsh", rather than "Small Toad Marsh", but the latter appears to be the more likely meaning, in my opinion. I would emphasize, though, that no one can give a definitive answer to the question of what the name means. The evidence is based on just a few scattered recordings of the name in the late 1300s, which may not record accurately how people spoke at the time, or what the name meant before then.