The double dagger is a punctuation mark that is used to indicate a footnote in a written text. It is also known as the "dagger" or "obelisk" symbol. There are several synonyms for the double dagger including the "obelus", "obelisk", "obelisk symbol", and the "cross-adorned dagger symbol". The obelus symbol is usually used in historical texts to mark the death of a person, while the cross-adorned dagger symbol is used to denote a footnote in a religious text. The use of these symbols in written texts has been around for centuries and is still widely used today.