anadiplosis (n.)

before vowels an-, word-forming element meaning: 1. "upward, up in place or time," 2. "back, backward, against," 3. "again, anew," from Greek ana (prep.) "up, on, upon; up to, toward; throughout; back, backwards; again, anew," from an extended form of PIE root *an- (1) "on, upon, above" (see on, which is the English cognate). In old medical prescriptions, ana by itself meant "an equal quantity of each."

1640s, "state paper, official document," from Latin diploma (plural diplomata) "a state letter of recommendation," given to persons travelling to the provinces, "a document drawn up by a magistrate," from Greek diploma "licence, chart," originally "paper folded double," from diploun "to double, fold over," from diploos "double" (see diplo-) + -oma, suffix forming neuter nouns and nouns that indicate result of verbal action (see -oma).

The main modern use is a specialized one, "a writing under seal from competent authority conferring some honor or privilege," especially that given by a college conferring a degree or authorizing the practice of a profession (1680s in English).

The plural is always -mas in the ordinary sense (certificate of degree &c.), though -mata lingers in unusual senses (state paper &c.) as an alternative. [Fowler]

Compare diplomacy, diplomatic.