1630s, Scottish form of Fr. cadet (see cadet
). Originally "person who runs errands;" meaning of "golfer's assistant" is 1851. A letter from Edinburgh c.1730 describes the city's extensive and semi-organized "Cawdys, a very useful Black-Guard, who attend ... publick Places
to go at Errands; and though they are Wretches, that in Rags lye upon the Stairs and in the Streets at Night, yet are they often considerably trusted .... This Corps has a kind of Captain ... presiding over them, whom they call the Constable of the Cawdys."
"small box for tea," 1792, from Malay kati a weight equivalent to about a pound and a third (in English from 1590s as catty), adopted as a standard mid-18c. by British companies in the East Indies. Apparently the word for a measure of tea was transferred to the chest it was carried in.