Tiernan is a distinctive boys' name in England & Wales, ranking #2335 in 2016 with 9 recorded births. This places Tiernan in the top 37% of ranked UK boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 1999 with 24 births ranking #697. In 2016, approximately 1 in every 36,881 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.