Tiernan is a distinctive boys' name in England & Wales, ranking #1110 in 1998 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 1998, approximately 1 in every 25,872 boys born was named Tiernan. FALLING Recent data shows the name is currently falling.