Casto
A surname that likely began as a nickname from Spanish/Latin casto, meaning “chaste” or “pure.”
The #4,293 most common surname in the United States (2010 Census) — about 1 in every 37,270 Americans shares it.
Etymology
Casto comes from Spanish and ultimately Latin castus, meaning “chaste,” “pure,” or “moral.” As a surname, it most likely began as a descriptive nickname for someone thought of as especially upright or reserved. The historical notes also show the word used as an epithet in medieval Spain, as in Alfonso el Casto (“Alfonso the Chaste”).
History
The evidence provided does not show a clear family-line origin for the surname itself, but it does confirm the word's long use as a sobriquet in Iberian history. In medieval records, Casto appears as an epithet attached to a ruler's name rather than as a hereditary surname, which is consistent with a nickname-based surname later forming from the same word. Modern bearers may therefore come from Spanish-speaking lineages where the nickname became fixed as a family name.
Origin
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Variant spellings
Fun fact
The word casto is still current in Spanish today, where it means “chaste” or “pure,” not just “upright.”
From the historical record
“sos ¡ otras fortificaciones. Casto. Honesto, opuesto o la sensualidad. Castizo, ha- blando del estilo. Castos. Plural del precedente. Castrillejo. Diminutivo de Castro.”
— Diccionario de los apellidos