"small box for tea," 1792, from catty (1590s), Anglo-Indian unit of weight, from Malay (Austronesian) kati, a unit of weight. The catty was adopted as a standard mid-18c. by the British in the Orient and fixed in 1770 by the East India Company at a pound and a third. Apparently the word for a measure of tea was transferred to the chest it was carried in.
"act as a caddy for a golfer," 1900, from an alternative spelling of caddie (n.). Related: Caddied; caddying.