Tiernan is a distinctive boys' name in United States, ranking #3840 in 2025 with 29 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 70.6%. In 2025, approximately 1 in every 58,899 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.