Green’s Dictionary of Slang

1. friendship, friendliness.

1876

Besant & Rice Son of a Vulcan II 152: The home life of that strange house where Jack and her father lived in bachelor chummery.

2. a small, private hotel.

1890		Dead Bird (Sydney) 12 July 2/2: [advert from UK press] A Widow Lady, just returned from India, will open a ‘chummery’ [...] for Gentlemen.
1950		‘Neville Shute’ Town Like Alice 35: A small private hotel [in Malaya] run by an Englishwoman which was, in fact, more or less a chummery for unmarried girls.