"Final vocabulary" is a term coined by Richard Rorty and explicated in Contingency, Irony, and Solidarity. A "final vocabulary" is a set of communicative beliefs whose contingency is more or less ignored by the bearer. These beliefs can concern anything; it does not matter whether they are shared by the entire human race or are entirely unique. For an ironist, a "final vocabulary" is always suspect.
Rorty, Richard. Contingency, Irony, and Solidarity. Cambridge: Cambridge University Press, 1989. ISBN 0-521-36781-6