Tiernan is a distinctive boys' name in England & Wales, ranking #1253 in 2002 with 12 recorded births. The name reached its all-time peak in 1999 with 24 births ranking #697. Since 1996, the popularity has increased by 20.0%. In 2002, approximately 1 in every 24,024 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.