Tiernan is a distinctive boys' name in United States, ranking #2677 in 2015 with 46 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 170.6%. In 2015, approximately 1 in every 41,658 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.