1590s, "to divide speech into distinct parts" (earlier in a now-obsolete sense "to formally bring charges against," 1550s), from Latin articulatus, past participle of articulare "to separate into joints," also "to utter distinctly," from articulus "a part, a member, a joint" (see article).
Generalized sense of "express in words" is from 1690s. In a physical sense, "to join, to attach by joints," it is attested from 1610s. Earlier sense "to set forth in articles" (1560s) now is obsolete or nearly so. Related: Articulated; articulating.
1580s in the speech sense, "divided into distinct parts," hence "clear, distinct" (1570s as "set forth in articles"), from Latin articulatus "separated into joints" (see articulate (v.)). Compare Latin articulatim (adv.) "distinctly, in clear sequence." Physical meaning "composed of segments united by joints" in English is from c. 1600. The general sense of "speaking accurately" is short for articulate-speaking (1829). Related: Articulately.