mid-14c., pronouncen, "to declare officially, proclaim, announce;" late 14c., "to speak, utter" (words, a language, etc.), "form or articulate with the organs of speech," from Old French prononcier "declare, speak out, pronounce" (late 13c., Modern French prononcer) and directly from Late Latin pronunciare, from Latin pronuntiare "to proclaim, announce; pronounce, utter," from pro "forth, out, in public" (see pro-) + nuntiare "announce," from nuntius "messenger" (from PIE root *neu- "to shout").
With reference to the mode of sounding words or languages, it is attested by 1610s (pronunciation in the related sense is attested from early 15c.). Meaning "make a statement," especially authoritative one (as in pronounce judgment) is from early 15c. Related: Pronounced; pronouncing.