The authors differ on the etymology of this surname. F. Miranda maintains that it derives from the transformation into a surname of the given name Clarus (in the feminine, Clara), used in the Christian Middle Ages in honour of several saints, especially through the cult of Saint Clare of Assisi, founder of the Poor Clares. The name comes from the Latin adjective clarus-clara-clarum, meaning "clear, manifest, famous, brilliant". Miranda adds that, in some cases, the surname could derive from affectionate or diminutive forms of toponymic nicknames that contain the root Chiara, present in many localities of Italy, thus linked to the place of origin of the first bearers.

V. Blunda, on the other hand, proposes a Sicilian dialectal origin: the surname would come from the expression èssiri in chiarènza, which means "to be without money" or, literally, "to be transparent". According to Blunda, it would have arisen as a nickname applied to someone in a situation of extreme poverty, a habitual practice in Sicilian surnames of a mocking tone, where the community's judgements about economic condition were crystallised into hereditary designations.

Miranda notes that the surname is concentrated mainly in Sicily —in the Catania, Agrigento, Palermo, Trapani, Syracuse, Messina, Caltanissetta and Enna areas—, with lesser presence in Lombardy, Piedmont, Liguria, Lazio, Tuscany and Veneto.