Tiernan is a distinctive boys' name in England & Wales, ranking #1156 in 2008 with 21 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has increased by 110.0%. In 2008, approximately 1 in every 16,161 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.