The phrase "do up brown" is spelled /du ʌp braʊn/. The first part of the phrase, "do up," means to fasten or button something, often referring to clothing. The second part, "brown," is a color. The use of the word "brown" in this phrase adds specificity to the action being described. It is unclear where this phrase originates, but it likely comes from a specific time and place where this particular way of speaking was common.