I've heard of commonwealth, but not commonweal. One definition of commonweal from the online dictionary is "commonwealth," though others are "the common welfare & public good." I saw the word used in this sentence: "We are to believe that two girls are such a big threat to the commonweal that they should be arrested on - get this - felony hate crime charges."

Obviously, the context supports "public good," though it could also support "commonwealth." Since Illinois isn't a commonwealth, clearly the author meant the former definition. How have you seen the word used?

The cathococ church has a publication called "Commonweal." It's not common, but a perfectly good word for that which is the "common good."

I hadn't put 2 and 2 together...obviously the word comes from the "common well" of mankind. The OED puts it way back to 1330, with this lovely quote from 1469: "a1469 Gregory's Chron. [an. 1450] (Camden 1876) 191 They [the Kentish insurgents] wente, as they sayde, for the comyn wele of the realme of Ingelonde." Ingelonde? That's great! Asa, there is also a quote from 1559 about the Christian (not specifically the Catholic) commonweal. I liked that quote, too: "in Strype Ann. Ref. I. App. viii. 20 The Christian commonweale is decayed." Life doesn't change, does it?