Tiernan is a distinctive boys' name in United States, ranking #3876 in 2018 with 28 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 64.7%. In 2018, approximately 1 in every 64,838 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.