[Ticonderoga34]

At local taverns, pubs, and bars, people drank from pint and quart-sized containers. A bar maid's job was to keep an eye on the customers and keep the drinks coming. She had to pay close attention and remember who was drinking in 'pints' and who was drinking in 'quarts,' hence the phrase 'minding your 'P's and Q's'.

I heard a different story about 'minding your 'P's and Q's'.

The story I heard was that the British Royal Navy used to give its sailors a rum ration everyday.

If a sailor was on duty, he got a pint of rum. If he was off duty, he got a quart of rum. Hence the saying, 'mind your 'P's and Q's'.

[elcid1970]

These sound like they were written by Woody Allen.

As for rum, we know what it means to be “groggy”. There was a Royal Navy captain whose trademark was his heavy coat made of coarse `grogram’. His crew nicknamed him “Old Grog”.

When he began cutting the sailors’ rum ration with water, the resulting drink was called `grog’ though not in his honor.