Séamus, is a male first name of Celtic origin. It is the Gaelic equivalent of the name James. The name James is the English New Testament variant for the Hebrew name Jacob. It entered the Irish and Scottish Gaelic languages from the French variation of the late Latin name for Jacob, Iacomus; a dialect variant of Iacobus, from the New Testament Greek Ἰάκωβος (Iákōvos), and ultimately from Hebrew word יעקב (Yaʻaqov), i.e. Jacob. Its meaning in Hebrew is "one who supplants" or more literally "one who grabs at the heel". When the Hebrew patriarch Jacob was born, he was grasping his twin brother Esau's heel.
Variant spellings include Séamas, Seumus, Shaymus, Sheamus and Shamus. Diminutives include Séimí, Séimín and Séamaisín. In the United States, the name "Shamus", of Yiddish origin, is sometimes used as a slang word for private detective.