This phrase is used to express the intention to finish an enterprise once it has been started, no matter much time, effort, or money this may entail.
It may have arisen originally from the fact that if one owed a penny, one might as well owe a pound (UK currency) as the penalties for non-payment were virtually identical in severity.
Or it may have been a reference to theft, saying that being arrested for stealing a small amount is just as bad as for a large amount, so you may as well steal a lot and hope to get away with it.
An equivalent expression is, ‘As well hanged for a sheep as a lamb,’ where it’s implied that you are stealing the animal. If the punishment for getting caught is the same, you may as well try for the largest possible reward, being the sheep.
And here is a play on words that makes me chuckle every time I read it:
The British Penny – European Union Directive No. 456179
In order to bring about further integration with the single European currency, the Euro, all citizens of the United Kingdom of Great Britain and Northern Ireland must be made aware that the phrase ‘Spending a Penny’ is not to be used after 31 December 2014.
From this date onwards, the correct term will be: “Euronating”.
It is hoped that this will be a great relief to everyone. If you have any questions, just give me a tinkle.