Shilling / bob

[Ewood27]

How did the pre-decimal shilling come to be called a 'bob'?

[Quizmonster]

'Bob' was used as slang for 'shilling' as far back as the 18th century. Its etymology is uncertain, the only vaguely possible link being with the 14th century French coin called a 'bobe', with an 'e'. However, the connection's a bit tenuous at best, according to the OED and Chambers.