Tiernan is a distinctive boys' name in United States, ranking #2007 in 2006 with 67 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 294.1%. In 2006, approximately 1 in every 30,673 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.