The title refers to the secrecy related to its founding, not any present-day secrecy. From the text:

> "It started as sort of secret colony," said Deborah-Jean Hoffman, a board member at the New Sweden Centre, which promotes the Delaware Valley's colonial history. "The Swedes weren't flag-planting like the French or the Spanish. The idea was to create an under-the-radar colony where the Dutch wouldn't see them."