Tiernan is a distinctive boys' name in United States, ranking #1787 in 2009 with 85 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 400.0%. In 2009, approximately 1 in every 23,333 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.