Tiernan is a distinctive boys' name in England & Wales, ranking #918 in 2000 with 17 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has increased by 70.0%. In 2000, approximately 1 in every 17,245 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.