I'm pretty sure Korean word 빵 was imported from Japanese way later than 1500s. Most likely during the colonial period (1910--1945) or shortly before that. As

I'm pretty sure Korean word 빵 was imported from Japanese way later than 1500s. Most likely during the colonial period (1910--1945) or shortly before that. As other comments explain, Japanese pan is pronounced not with [n] but with a uvular nasal, which is close to "ng" in English "king", so Japanese word-final "n" is commonly imported to Korean as ㅇ ("ng").