Fionn is a distinctive boys' name in United States, ranking #5118 in 2003 with 15 recorded births. This places Fionn in the top 40% of ranked US boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 2018 with 40 births ranking #2963. In 2003, approximately 1 in every 131,685 boys born was named Fionn. FALLING Recent data shows the name is currently falling.