Wiktionary
a. (context obsolete English) earlier, former n. (context in combination English) A person who advocates the primacy of the named entity (who puts it first)
Usage examples of "firster".
Organizations publicly claiming responsibility included the Earth- Firsters, the Red Army Faction, the Islamic Jihad, the now underground Fusion Energy Foundation, the Sikh Separatists, Shining Path, the Khmer Vert, the Afghan Renaissance, the radical wing of Mothers Against the Machine, the Reunified Re unification Church, Omega Seven, the Doomsday Chiliasts (although Billy Jo Rankin denied any connection and claimed that the confessions were called in by the impious, in a doomed attempt to discredit God), the Broederbond, El Catorce de Febrero, the Secret Army of the Kuomin-tang, the Zionist League, the Party of God, and the newly resuscitated Symbionese Liberation Front.
Organizations publicly claiming responsibility included the Earth Firsters, the Red Army Faction, the Islamic Jihad, the now underground Fusion Energy Foundation, the Sikh Separatists, Shining Path, the Khmer Vert, the Afghan Renaissance, the radical wing of Mothers Against the Machine, the Reunified Reunification Church, Omega Seven, the Doomsday Chiliasts (although Billy Jo Rankin denied any connection and claimed that the confessions were called in by the impious, in a doomed attempt to discredit God), the Broederbond, El Catorce de Febrero, the Secret Army of the Kuomintang, the Zionist League, the Party of God, and the newly resuscitated Symbionese Liberation Front.
That morning in Radcliffe Yard, rival student groups had set up stalls and handed out leaflets, the Interventionists passionately advocating that America should enter the war, the America Firsters arguing the opposite whith equal fervour.