Tiernan first appears in the U.S. registration record in 1985. Its popularity climbed over the following decades. In 2007, 86 babies received the name (ranked #1738). Today it sits well outside the top 1,000 (around #3737), with roughly 33 babies named Tiernan each year. Tiernan's usage has held roughly steady recently. In total, around 1,647 babies have been registered with this name since 1880.