Declan is the Anglicized form of the Irish name Deaglán. St. Declan was one of the first missionaries to bring Christianity to Ireland, preceding St. Patrick. Originally from Wales, he founded the monastery of Ardmore in Ireland.

Landon is a popular surname name; it's been dropping slightly in recent years but has surpassed its once more popular rhyming cousin Brandon. For some it may bring back nostalgic memories of Little House on the Prairie 's understanding Pa, played by Michael Landon.