Guillermo is a distinctive boys' name in United States, ranking #690 in 2013 with 348 recorded births. The name reached its all-time peak in 1998 with 693 births ranking #369. Since 1996, the popularity has decreased by 49.7%. In 2013, approximately 1 in every 5,435 boys born was named Guillermo. STABLE Recent data shows the name is currently stable.