The story
From common (“public”) + wealth (“well-being”). From c. 1450 as common wele (commonweal). In the form common-wealth (common welthe) from c. 1520, used by Tyndale in the sense "secular society" in particular, for which other authors preferred publike weal. Also from the 1520s treated as a synonym or loan-translation of res publica (republic) (Rollison 2017:67f).
Etymology from Wiktionary, CC BY-SA 4.0.