Castor is a distinctive boys' name in United States, ranking #5336 in 2015 with 17 recorded births. This places Castor in the top 38% 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 2015, approximately 1 in every 112,721 boys born was named Castor. RISING Recent data shows the name is currently rising.