Churlish \CHUR-lish\ , adjective;
1. Boorish or rude
2. Of a churl; peasantlike
3. Stingy; mean
4. Difficult to work or deal with, as soil
Churlish derives from late Old English cierlisc ("of or pertaining to churls"). Churl comes from Old English ceorl ("peasant, freeman, man without rank") from Proto-Germanic *kerlaz. In Middle English churl had different meanings, including "man of the common people," "a country man," "husbandman," and "free peasant." By 1300 it had evolved to mean "bondman, villain" or "fellow of low birth or rude manners." By the late 14th century churlish had come to mean "deliberately rude."
Churl is not alone in its transition from something like "common man" to "rude." Boor and villain have also taken the same route.
Boor dates to the 13th century from Old French bovier ("herdsman"), which derives from Latin bovis, the genitive of bos ("cow, ox"). The word fell out of use in English for a while, but was re-introduced via Dutch boer in the 16th century. Boer come from Proto-Germanic *buram ("dweller, farmer") and, like bos, ultimately derives from Proto-Indo-European *bhu-. The negative connotation doesn't appear in print until the 1560's as boorish and comes from the notion of 'clownish rustics.'
Villain dates to the 1300's as "base or low-born rustic" from Anglo-French and Old French villain, which derives from Middle Latin villanus ("farmhand") based on Latin villa ("country house"). Villa comes from Proto-Indo-European *weik- ("clan").