Thelonious first appears in the U.S. registration record in 1960. Its popularity climbed over the following decades. In 2017, 23 babies received the name (ranked #4448). Today it sits well outside the top 1,000 (around #5419), with roughly 18 babies named Thelonious each year. Thelonious's usage has held roughly steady recently. In total, around 455 babies have been registered with this name since 1880.