Green’s Dictionary of Slang

elephant and castle n.

[rhy. sl.]

1. the anus [arsehole n. (1) (pron. ‘arssle’)].

[UK]S.T. Kendall Up the Frog.
[UK]D. Powis Signs of Crime 182: Elephant (& Castle) Anus.
[UK]J. Morton Lowspeak.
[UK]R. Puxley Cockney Rabbit.
[Aus]Age (Melbourne) 7 Dec. 130/7: ‘You’re an Elephant and Castle’.
[UK]B. Dark Dirty Cockney Rhy. Sl.

2. a parcel.

[UK]J. Gosling Ghost Squad 24: Thieves’ argot, spoken properly, is a foreign language which needs to be learned [...] Among the words and phrases derived from rhyming slang are: [...] ‘Elephant’ equals ‘Elephant and Castle’ (pronounced ‘Carsel’) which means a parcel.