Meaning

adjective of textures that are rough to the touch or substances consisting of relatively large particles

adjective lacking refinement or cultivation or taste

adjective of low or inferior quality or value; - Shakespeare

originAdjectival use of course that diverged in spelling in the 18th century. The sense developed from '(following) the usual course' (cf. of course) to 'ordinary, common' to 'lacking refinement', with 'not fine, granular' arising from its application to cloth. Compare the development of mean.

Etymology from Wiktionary, CC BY-SA 3.0