In Conan Doyle's Holmes short story The Adventure of the Reigate Squire, the murder victim is a coachman named William Kirwan. Conan Doyle seems to have found this name in reports of a very colourful real murder which was dominating the London newspapers at the time.

The real William Kirwan was a respectable London doctor who unaccountably turned up in Southwark in October 1892, so incapitated that he could barely walk, and with an alcoholic street whore as his only companion. He wandered blithely round the most dangerous streets in London for several hours before - inevitably - being robbed and murdered in an alley. You can read the full story here: http://www.planetslade.com/william-kirwan.html. 

Reigate Squire first appeared in The Strand's issie of June 1893, which suggests Conan Doyle may well have been working on it - or at least planning it out - when Kirwan's death and his killers' trial were filling the London papers in October and November of 1892. Reporters nicknamed it The Borough Mystery, and no-one could ever understand how Kirwan had allowed himself to be so vulnerable in such a dangerous area. The playwright Arthur Wing Pinero later wrote a play based quite precisely on Kirwan's case (Dr Harmner's Holidays), but he came no closer to explaining the real Kirwan's conduct than anyone else.

There's no connection between the plot of Reigate Squire and the real Kirwan's murder, but the timing does suggest that Conan Doyle borrowed his victim's name from the case. For all I know this may already be common knowledge among Holmes experts, but I'd not come across the link before and I thought it was interesting enough to mention here.

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