Deklan is a phonetic spelling of Declan, the Irish Deaglán, a name whose meaning is uncertain and is usually explained as "full of goodness". Saint Declan of Ardmore is said to have brought Christianity to County Waterford before Saint Patrick arrived. Deklan peaked at number 1053 in 2018 and has fallen to number 2399 in 2025, while Declan remains a top 100 name.