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Pony is a slang word in UK, not great choice for name.

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Yes it does mean £25, but rarely used any more however the alternative is

Meaning: Rubbish; nonsense, or 'of poor quality'. Often shortened just to 'pony'.

What's the origin of the phrase 'Pony and trap'? This is Cockney rhyming slang - pony and trap -> crap.