One for the road
A drinking proposition that urges a final drink before the journey home. It was originally a British expression that soon took hold on both sides of the Atlantic, and around the English-speaking world. It is first attested from the 1930s, when most people used to walk home, but these days, police forces prefer ‘none for the road’ if driving home. In Britain and elsewhere, it is sometimes expressed as ‘one for the frog’, which derives from rhyming slang, frog and toad/road.