going to see a man about a dog

[justineo]

anyone know where this comes from?  My grandad used to say it if he didn't want us to know where he was going

[Octavius]

From The Flying Scud in 1866:

http://www.worldwidewords.org/qa/qa-see1.htm

[silly moo]

Often used these days as a euphemism for going to the loo.

[Clanad]

I'm sure it must be a regional thing, but here in the western U.S. the phrase is "have to see a man about a horse"... and the meaning is, as silly moo states, the same here...

[Clare A]

Also as a euphemism for going to the pub!

[rachaelersk]

my grandad used to say it if he was off to the loo and didnt want to tell us.