Tiernan is a distinctive boys' name in England & Wales, ranking #2952 in 2025 with 7 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has decreased by 30.0%. In 2025, approximately 1 in every 38,848 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.