Guillermo is a distinctive boys' name in United States, ranking #619 in 2012 with 392 recorded births. The name reached its all-time peak in 1998 with 693 births ranking #369. Since 1996, the popularity has decreased by 43.4%. In 2012, approximately 1 in every 4,838 boys born was named Guillermo. STABLE Recent data shows the name is currently stable.