Tiernan is a distinctive boys' name in United States, ranking #2371 in 2000 with 41 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 141.2%. In 2000, approximately 1 in every 47,901 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.