Tiernan is a distinctive boys' name in England & Wales, ranking #3996 in 2017 with 4 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has decreased by 60.0%. In 2017, approximately 1 in every 80,716 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.