Castor is a distinctive boys' name in United States, ranking #7728 in 2005 with 9 recorded births. This places Castor in the bottom 42% of ranked US boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 2016 with 29 births ranking #3702. In 2005, approximately 1 in every 221,905 boys born was named Castor. RISING Recent data shows the name is currently rising.