Prenominal adjective borrowed into Arabic from Persian?

A major interest of mine lately is the way in which lexical borrowings can affect syntax, dragging bits of the source language's word order with them. I came across what looks like a nice example of this in a book on Gulf Arabic. In Kuwaiti dialect, as in all dialects of Arabic, adjectives normally follow the noun. However:

The (Persian) adjective kooš precedes the noun it qualifies. It does not occur in association with defined nouns. It is not inflected for gender or number. Thus:
    kooš walad, bint    a good boy, girl
(T. M. Johnstone, Eastern Arabian Dialect Studies, London: Oxford University Press 1967, p. 147.)

Only trouble is, my Persian grammar doesn't say anything about the Persian adjective in question being pre-nominal, and virtually all adjectives in Persian are post-nominal. Does anyone know more about this?