(The name is spelled in various ways, Weigandt, Wiegandt, Weigand, Wigand, and Weygand)
Weigand is a sur-name, certainly Germanic in origin, and said by some sources to be a variant of Wiegandt though the phonetic pronunciation of the two should be quite different, at least to a non-German speaker - i.e. “ei” = "eye", and “ie” = "eee". Perhaps the Weygand “ey”, frequently heard as “aaa”, is a phonetic compromise when the name is Anglicized?
According to Wikipedia, the the name is said to be from Old High German and mean the holder of the name was a fighter or a warrior. Alternatively, another source states that the name dates to the Middle Ages and is originally from the Breton language (a regional dialect of Brittany) and means “noble and worthy.” In both cases it is a descriptive surname or an occupational surname. This would mean that using a pre-name, such as “von” (meaning "of" or “from” in German naming usage), would not normally be appropriate. None of the original official records relating to our Weygand family use a pre-name and most clearly use the spelling of “Weygand” back into the 18th century. So the idea that our family name may have been, early on, “von Weygand” appears to not be the case.
Our Weygand Family immigrant ancestor was Karl Georg (Charles George) Weygand who in 1879 emigrated from either Mannheim, Grand Duchy of Baden, or from the area around Darmstadt (probably Heppenheim), Province of Hesse-Nassau of the Kingdom of Prussia. He was in the company of his brother Friedrich Karl. Their mother, Emilie (Lay) Weygand, and several of their siblings emigrated in 1881, probably from Mannheim where the family was known to have been living after the death of their father, Johann Ludwig Weygand in 1874.
Our Weygand ancestry can be readily followed back to Johann Valentin Weygand who lived 1711 to 1793 in Hesse-Darmstadt, a Hessian state of the Holy Roman Empire. Since the Weygand name is said to date to the Middle Ages, a researcher with a better grasp of the German language would undoubtedly be able to trace the family back to a much earlier time.
In the meantime, it is only appropriate to acknowledge the research done and memories shared by members of the Weygand Family to this point (research is continuing): Lillian E. (Weygand) Doran, Barbara M. (Weygand) Blackburn, Andrea (Weygand) King, and most especially, Norman Charles Reuel.
The links above on the left will direct you to the person pages of the members of our Weygand Family, but a reasonable starting point would be with Dorothy Margaret Weygand, maternal grandmother of The 3 Tracys born c. 1975.