A Roman walks into a bar and asks for a martinus.

This clever bar joke serves up its humor with a healthy shot of wordplay, specifically a linguistic pun rooted in Latin grammar. When the Roman asks for a "martinus," he's playfully applying ancient Roman language rules to a modern cocktail. The "-us" ending in Latin often denotes a singular noun, making "martinus" a perfectly logical, albeit anachronistic, request for one drink.

The punchline then brilliantly reveals the joke's core: the Roman implies that "martini" – the common name for the drink – would, by his linguistic logic, signify a plural or a "double" serving. It’s a delightful blend of historical context and cocktail culture, imagining a toga-clad patron sticking to their grammatical guns. The humor comes from this unexpected clash of ancient language structure with a contemporary bar order, making us chuckle at the Roman's commitment to linguistic consistency.