Over the past 110 years, 38 742 boys and 11 girls have been named Declan. The name Declan ranks 519th in the United States among the most common names for boys. For the first time more than ten times newborns were named Declan in 1968. The peak of popularity of the name Declan came in the 2000s and 2010s. You can see absolute numbers and relative numbers on the chart. Indicators per 100K more accurately assess the popularity of the name.