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 Earlier sense "to set forth in articles" (1560s) now is obsolete or nearly so.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.