When did the shellback initiations begin?

Shellback initiations, which celebrate a sailor's crossing of the equator, have roots that trace back to ancient maritime traditions. The specific practices began to formalize in the 19th century, particularly within the U.S. Navy, as a rite of passage for sailors. This initiation involves various rituals and ceremonies, marking the transition from "pollywog" to "shellback" upon crossing the equator.