Tiernan is a distinctive boys' name in England & Wales, ranking #1761 in 1997 with 6 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has decreased by 40.0%. In 1997, approximately 1 in every 52,407 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.