Tiernan is a distinctive boys' name in United States, ranking #1923 in 2011 with 73 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 329.4%. In 2011, approximately 1 in every 26,014 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.