Tiarnan is a distinctive boys' name in United States, ranking #8375 in 1998 with 7 recorded births. This places Tiarnan in the bottom 26% of ranked US boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 2002 with 8 births ranking #8370. In 1998, approximately 1 in every 273,045 boys born was named Tiarnan. FALLING Recent data shows the name is currently falling.