Wordorigins.org

A truck farm has nothing to do with motorized cargo vehicles. The truck in truck farm comes from the noun meaning trade or barter, a word borrowed from the Anglo-Norman truke in the 14th century. From Richard Hakluyt’s 1553 The Principall Navigations, Voiages and Discoueries of the English Nation (published in 1598):

No commutation or trucke to be made by any of the petie marchants, without the assent abouesaid.