From Lithuanian legends about Neringa and Naglis
In Lithuanian folklore, Neringa is a beautiful, gentle giantess who built a mound of sand to keep the stormy waves of the Baltic sea at bay and protect the village and the people who live in it. One day, she catches the eye of Naglis, a dragon (some legends call him a sea serpent) living nearby, who madly falls in love with her. When Naglis realizes that his love is unrequited, in his wrath and his grief, he starts eating the fishermen living in Neringa's village one by one. Neringa is greatly saddened by these occurences, and so she creates a strip of sand between the bay and the Baltic sea, which would seperate her and her subjects from the dragon forever.
The exact origin and meaning of the name are uncertain, however some scholars believe that it is derived from Old Prussian neria
"to dive (like a swimmer)".
The name became briefly popular in 1923 when the Curonian Spit, and with it the resort city Neringa, was incorporated into Lithuania.
Its designated name day is August 20.