Double Dagger

Style manuals agree on the first three footnote marks and then scatter. Asterisk, dagger, double dagger — after that, Bringhurst gives section sign, parallels, pilcrow; the US Government Publishing Office stops at the section sign and explicitly forbids the number sign as a reference mark, on the grounds that it already means too many other things; a nineteenth-century American history text runs asterisk, dagger, double dagger, number sign, parallels. Bringhurst is candid about the mess. Beyond the first three, he writes, the order "is not familiar to most readers, and never was." His own advice is to give up and use numbers.

The mark's ancestor was an editorial weapon. The obelus — from the Greek for a sharpened stick or roasting spit — was devised by Zenodotus at Alexandria to flag words and passages in Homer that he judged spurious. The metaphor was skewering: this line should probably be cut. Origen later reused the mark in the Hexapla with an inverted criterion, marking text that was missing from the Hebrew.

The single dagger picked up a second career as a death mark, placed before or after a name to show the person has died, or paired with an asterisk to bracket birth and death years. Biologists use it the same way for extinct taxa. The double dagger, having no such sideline, stayed in the footnotes.