It has been a male first name in Italy, Austria, Germany, Switzerland, Argentina, the Low Countries, Scandinavia, Spain, Portugal and Latin America, as well as other places with migration from those.
Regarding origins, there are most likely homonymous forms of it, that is, from several etymological predecessors but now seeming to be the same name.
Another likely homonym is the Italian Guido from a latinate root for "guide".
The slang term Guido is used in American culture to refer derogatorily to an urban working-class Italian or Italian-American male who is overly aggressive or macho with a tendency for certain conspicuous behaviour.
[3] It may also be used as a more general ethnic slur for working-class urban Italian Americans.