Ildefonso is a distinctive boys' name in United States, ranking #5811 in 1997 with 10 recorded births. The name reached its all-time peak in 1997 with 10 births ranking #5811. Since 1996, the popularity has increased by 42.9%. In 1997, approximately 1 in every 188,509 boys born was named Ildefonso. STABLE Recent data shows the name is currently stable.