Thaddeus is the Greek form of the Aramaic Thaddai, a name of uncertain meaning that is usually explained as "heart" or "courageous". It belongs to the apostle Jude Thaddeus, and the Polish patriot Tadeusz Kosciuszko, who fought in the American Revolution, gave it a place in US history. Thaddeus has been in the US top 1000 since 2010, peaked at number 640 in 2016 and ranks number 798 in 2025.