Tiernan is a distinctive boys' name in United States, ranking #3220 in 2016 with 36 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 111.8%. In 2016, approximately 1 in every 52,700 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.