Tiernan is a distinctive boys' name in United States, ranking #1866 in 2005 with 69 recorded births. This places Tiernan in the top 14% of ranked US boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 305.9%. In 2005, approximately 1 in every 28,944 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.