The meanings of "rough, low quality" and "last, final" feel UNrelated to me. What semantic field underlies these meanings? Just because something is "last, final" doesn't mean it's "rough, low quality". English has the adage "save the best for last"!
They are different words, but coincidentally have the same form / pronunciation. This is why they're listed as "Etymology 1" and "Etymology 2": having different origins (etymologies). This is called '동음이의어' in Korean, or 'homonyms' in English. An example in English would be 'bark' (the sound of a dog) and 'bark' (the skin of a tree).