Tiernan is a distinctive boys' name in United States, ranking #4839 in 2020 with 20 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 17.6%. In 2020, approximately 1 in every 86,253 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.