Tiernan is a distinctive boys' name in England & Wales, ranking #3334 in 2020 with 5 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has decreased by 50.0%. In 2020, approximately 1 in every 57,798 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.