Trading the Cable

"Cockamamie. That's a word you generation hasn't embraced yet. You ought to use it once in a while to keep it alive."
--Frank Horrigan (In the Line of Fire)

They say you learn something new every day. Saw this headline this am and couldn't figure what 'cable' meant in the context.

Turns out it refers to exchanges between the British pound and the USD. 

When transatlantic cable was stretched across the ocean floor in the mid 1800s to connect telegraph services between the England and the US, transactions between the two currencies became known as 'trading the cable.'

Obviously, this is no longer popular slang as it took me several decades before I heard it.

Interesting nonetheless. And I hope to put my newly discovered lingo to work soon.