Ildefonso is a distinctive boys' name in United States, ranking #11165 in 2006 with 6 recorded births. This places Ildefonso in the bottom 21% of ranked US boys' names for the year. Its actual usage is classified as Rare. The name reached its all-time peak in 1997 with 10 births ranking #5811. Since 1996, the popularity has decreased by 14.3%. In 2006, approximately 1 in every 342,520 boys born was named Ildefonso. STABLE Recent data shows the name is currently stable.