I saw a photograph of Chris Robshaw, the Harlequins captain, in the paper yesterday sporting a magnificent shiner, and naturally started to wonder where the term originated.
Consulting Etymonline revealed a date (1904) but no explanation.
I also turned up a question on Answerbag stating that it is derived from the derogatory word shiner meaning a black person. The dates given in Etymonline make this quite plausible, but Green's Dictionary of Slang dates the first usage of shiner for black eye at 1797, which would tend to militate against this etymology.
The comments also suggest the name derives from the shiny skin of a black eye; I have some personal experience of these things and I can't say I've ever noticed.
Urban Dictionary has a different explanation:-
Term is of Irish origin where it was a punishment for not keeping machinery shiney delivered from the boot of a British officer.
I can't say I'm convinced by this.
So, does anyone know why a black eye is called a shiner?