A Locale's language may include designation of a particular script (per the IETF BCP 47 spec) using an ISO 15924 alpha-4 script code.
A list of example languages available on Mac OS X:
az-Cyrl "Azerbaijani (Cyrillic)"
ms-Arab "Malay (Arabic)"
sr-Latn "Serbian (Latin)"
tk-Cyrl "Turkmen (Cyrillic)"
tt-Cyrl "Tatar (Cyrillic)"
tt-Latn "Tatar (Latin)"
uz-Arab "Uzbek (Arabic)"
uz-Latn "Uzbek (Latin)"
zh-Hans "Chinese (Simplified)"
zh-Hant "Chinese (Traditional)"
As of JDK-6990452, system properties are provided to reflect the script:
On Mac OS X (and perhaps elsewhere?), these properties aren't set, but they should be.
This was uncovered during work on JDK-7131356.