I wondered about this, myself
This is from the archives of an etymological site Take Our Word For It
(no longer active?), at http://www.takeourword.com/Issue009.html
"A reader recently enquired about the origin of The Elephant and Castle, the name of a square in London. This falls outside the normal scope of Words to the Wise but it raises several interesting topics so I thought I'd talk about it here.
"The square takes its name from The Elephant and Castle pub which stands on one of its corners. The pub has a splendid old inn-sign showing an elephant equipped for battle with a castellated howdah on its back, rather like a castle from an old chess-set. . . .
"So, back to the pub. It is quite possible that its name comes, for whatever reason, from this image of a war-elephant. There is another suggestion, however, that it is a corruption of the Spanish phrase La Infanta de Castilia.
Whether this is true or not, it is impossible to say. There has been an inn of that name on the same site for many hundred years and there is no longer sufficient evidence to decide."
(While we were in the UK, anher
said repeatedly he'd like to know how the Tube station Elephant and Castle got its name. Well, now he knows.)