Tiernan is a distinctive boys' name in United States, ranking #2015 in 2002 with 55 recorded births. The name reached its all-time peak in 2007 with 86 births ranking #1738. Since 1996, the popularity has increased by 223.5%. In 2002, approximately 1 in every 35,299 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.