Tiernan is a distinctive boys' name in United States, ranking #1832 in 2004 with 68 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 300.0%. In 2004, approximately 1 in every 29,188 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.