Declin is a masculine given name emerging as a modern variant of the Irish Gaelic Declán, which combines deagh (“good”) and lán (“full”) to mean “full of goodness.” Historically anchored by Saint Declán of Ardmore, a fifth-century Irish missionary, the name carries connotations of steadfast leadership and quiet resolve. Phonetically rendered /dɪˈklɪn/ (dih-KLIN), it presents a streamlined alternative to more common forms. In the United States, Declin maintains a consistently low profile, with annual registrations fluctuating between six and fourteen newborns from 2014 through 2019 and popularity ranks hovering between 880 and 924. This analytical overview underscores its etymological depth, historical resonance and statistical rarity—qualities likely to appeal to parents uninterested in nursery uniformity.