British. a variety of hard mint candy. (http://dictionary.reference.com/browse/humbug)
"In the larder off the kitchen, tins of bully beef and peas and pears sat on shelves beside sardines and sugar and a big jar of humbugs, of which the late Mrs. Docherty had been legendarily fond."
- M. L. Stedman, The Light Between Oceans (2012)