Definition from Wiktionary, the free dictionary
Earliest recorded use is by Admiral Fisher, later First Sea Lord, in a 1901 letter.
- (idiomatic, UK) The appointment of a person by rotation or promotion, on the basis of length of service (it being that person's "turn") rather than merit or level of qualification.
- He will be appointed on the principle of Buggins's turn.
- 1919, Memories, John Fisher (reprinting a 1917 letter to him from an unnamed Privy Councillor) 
- I remembered your old saying "Some day the Empire will go down because it is Buggins's turn."'