Gilman
A surname most often traced to a medieval diminutive of Guillaume, the French form of William.
The #3,003 most common surname in the United States (2010 Census) — about 1 in every 25,845 Americans shares it.
Etymology
In the historical surname sources, Gilman is usually explained as coming from the French diminutive Guillemin, ultimately related to Guillaume, the French form of William. The first element seen as Gil-/Guill- reflects a medieval French naming pattern rather than any connection with a place or with the word "gill." In other words, the name is generally understood as a descendant of William through French nickname forms.
History
19th- and early-20th-century surname writers note that Gilman was one of several English surnames shaped by French forms of William, and they warn against confusing it with unrelated names that only look similar. The spelling was also influenced by variants such as Gillemin, Gilmyn, and related forms. In English-speaking countries the surname later became established independently as a hereditary family name.
Origin
Regions
Variant spellings
Fun fact
The surname was long liable to be misread as if it had something to do with a "gill," but historical scholars specifically rejected that explanation.
From the historical record
“which have no connexion with the word. One is Gillman or Oilman, not a dweller in a gill, but an imitative variant of Gillemin, or Gilmyn, a popular font-name in the surname period (v. Gilman). Another is Godliman, for Godalming; 1696-7. Mairied— Samuell Carr and AMNE Hall, of Godlyman, co, Surrey: Reg. St. Dionis…”
— A Dictionary of English and Welsh Surnames, with special American instances