甜 is sweet, 豉 is salted fermented beans and 油 is oil (also used in 香油sesame oil), so 豉油 is sweet salted fermented bean oil.
About This Dish
Sweet soy sauce conists mostly of wheat, so it's also known as Tianmian sauce, which means sweet flour sauce, and not suprisingly very thick, so it's also known as sweet wheat paste.