Counsel / council

Subito consilium cepi ut ante quam luceret exirem, ne qui conspectus fieret aut sermo, lictoribus praesertim laureatis. De reliquo neque hercule quid agam neque quid acturus sim scio; ita sum perturbatus temeritate nostri amentissimi consili. Tibi vero quid suadeam, cuius ipse consilium exspecto? Gnaeus noster quid consili ceperit capiatve nescio adhuc, in oppidis coartatus et stupens. Omnino, si in Italia consistat, erimus una; sin cedet, consili res est.

— Cicero, Letter to Atticus VII.10.

Five consecutive sentences, all using the word consilium, but in different senses, corresponding to shades of the English words counsel and council: respectively, 'I took counsel', 'our most insane council', 'whose counsel I am waiting for', 'whose counsel he took', 'a matter for the council'. From the OED's entries on counsel and council:

E. counsel, from L. consilium consultation, plan decided on as the result of consultation, advice, counsel, advising faculty, prudence; a deliberating body, a council of state, war, etc.; a counsellor. . . con- together + *sal- a root found also in consul, consulto, and prob. cognate with Skr. sar- to go.

E. council, from L. concilium (f. con- together + cal- to call) a convocation, assembly, meeting, union, connexion, close conjunction; sometimes an assembly for consultation, in which sense it became confused with consilium an advisory body. . . In English, the two words were, from the beginning, completely confused: conseil was frequently spelt conceil; concile was spelt consile and conceil; and the two words were treated as one, under a variety of forms, of which counseil, later counsel, was the central type. In the 16th c. differentiation again began: councel, later council, was established for the ecclesiastical concilium, F. concile; and this spelling has been extended to all cases in which the word means a deliberative assembly or advisory body (where L. has consilium, Fr. conseil), leaving counsel to the action of counselling and kindred senses. The practical distinction thus established between council and counsel does not correspond to Latin or French usage.

I love this, the deepest level of etymology, where one comes to realise that a word can indeed have more than one root. It is almost to return to the earliest etymologists, who were quite happy to find a different origin for each aspect of a word's meaning. Robert Grosseteste, for instance—and admittedly a relatively late one—in book three of his 1230 Hexaemeron, offers three explanations of caelum, 'sky': 1. from caelatum, 'engraved', because it is engraved with stars, 2. from celare, 'to hide', because it is hidden at night, and 3. from the bastard Greek-Latin casa heliou, 'house of the sun'.