A Man about a Horse/Dog

[Wilcox, Rose (ZB5646)]

An informal search of the Internet brought the inconclusive results:

1.
>From the Phrase Finder
http://www.shu.ac.uk/cgi-bin/tp_post3.cgi?=159900

Go to see a man about a dog

Warning that you are about to do something in a secretive manner and that
you don't want to talk about it until later.

2.
>From an advertisement for an "offroad commode"
http://www.offroadcommode.com/

So, you're out in the woods and "Nature calls", "you've got to see a man
about a horse", you need a "potty break".

3.
>From an "MSTing" (Mystery Science Theatre fanfic)

http://members.tripod.com/~Litterae/sinmst5.html
Crow: [As Maeve] ...I've got to see a man about a horse.

*"I'll be back as well," Sinbad said and followed where Maeve had
*left.

Joel: Ah, the call of nature.

4.
from a Terry Prachett FAQ
http://www.cs.hut.fi/~pno/Fiction/apf/apf7.mvpic.html

'Not now, man,' snapped the Archchancellor. 'Got to see a man about a horse,
what?'"

In previous versions of the APF, I had a bit of trouble finding out just
what this phrase refers to, having received several conflicting reports.

The general consensus now appears to be, however, that the phrase originates
from "got to see a man about a dog", an English euphemism for going to the
lavatory

5.
>From The Stoners' Dictionary Init
http://www.mentalfx.com/dictionary/

"Got to see a man about a dog." Means you have to go and buy a bag but don't
want someone in the room to know what you are talking about.