Guillermo
A Spanish-language surname derived from the given name Guillermo, itself the Spanish form of William.
The #9,581 most common surname in the United States (2010 Census) — about 1 in every 90,995 Americans shares it.
Etymology
Guillermo is ultimately from the Germanic personal name that became William in English. The older name was built from elements meaning roughly "will, desire" and "helmet, protection," so the traditional sense is often given as "helmet of resolve" or a similar protective meaning. As a surname, Guillermo is best understood as a patronymic or family-name form taken from the Spanish given name.
History
The name is common as a Spanish given name, and in some cases it has also been used as a hereditary surname. Its presence in the Americas is largely tied to Spanish-speaking populations and migration from Spain and Latin America. Because it overlaps with a very common first name, surname use may have arisen independently in multiple families.
Origin
Regions
Variant spellings
Fun fact
The same old Germanic name behind Guillermo also produced William, Guillaume, Wilhelm, and Guglielmo across Europe.
From the historical record
“315 Guillermo, m. Span. Teu. helmet of resolution, 315 Guillette, f. Fr. Teu. helmet of resolu- tion, 315”
— History of Christian Names