This word is still very much alive in it’s traditional heartland of India. Lunches are often by train, perhaps 20 or 30 miles to their places of work by tiffin-wallahs, each three-tiered tiffin-carrier probably passing through several hands in the process. The word has also long been used for any light meal taken during the day, except breakfast.
Tiffin is a word that perhaps more than any other evokes British India. It entered the language at the very beginning of the nineteeth century, perhaps because the fashion for eating dinner mid-afternoon was giving way to a main meal taken later in the day, requiring a lighter midday meal and a name for it. Why the much older luncheon or lunch wasn’t used isn’t clear. Instead, the English in India borrowed tiffing, an old English dialect or slang word for taking a little drink or sip (I forbear from suggesting that the habit among some sahibs of drinking their lunch had something to do with the popularity of the term.)
An early example of tiffin is from a guide book, Cordiner’s Ceylon, of 1808: “Many persons are in the habit of sitting down to a repast at one o’clock, which is called tiffen, and is in fact an early dinner”.