1530s, "dutiful or courteous approach," from address (v.) and from French adresse (13c., from the verb in French). Meaning "power of directing one's actions and conduct" is from 1590s. Meaning "act or manner of speaking to" is from 1670s. Sense of "formal speech to an audience" (Gettysburg Address, etc.) is from 1751. Sense of "superscription of a letter" (guiding it to its destination) is from 1712 and led to the meaning "place of residence" (from c. 1816). Transferred use in computer programming is from 1948. Middle English had a noun addressing "control, correction" (late 14c.).
late 14c., declamacioun, "composition written to be declaimed," from Latin declamationem (nominative declamatio) "exercise in oratorical delivery; declamation;" in a bad sense, "loud, eager talking," noun of action from past-participle stem of declamare "to practice public speaking, to bluster," from de-, here perhaps an intensive prefix (see de-) + clamare "to cry, shout" (from PIE root *kele- (2) "to shout"). Meaning "a public harangue or speech" is from 1520s; sense of "act of making rhetorical harangues in public" is from 1550s.
"having the power of expressing strong emotions in vivid and appropriate speech; able to utter moving thoughts or words," late 14c., from Old French eloquent, from Latin eloquentem (nominative eloquens) "speaking, having the faculty of speech; eloquent," present participle of eloqui "to speak out" (see eloquence). Related: Eloquently.
1550s, in grammar, "to state the part of speech of a word or the words in a sentence," a verbal use of Middle English pars (n.) "part of speech" (c. 1300), from Old French pars, plural of part "a part," from Latin pars "a part, piece" (from PIE root *pere- (2) "to grant, allot") in the school question, Quae pars orationis? "What part of speech?" Transferred (non-grammatical) use is by 1788. Pars also was a common plural of part (n.) in early Middle English. Related: Parsed; parsing.