What it means
Tot pulls a neat little double shift in British and Commonwealth English. It can mean a very small child, especially a toddler, or a small measure of spirits, like a tot of whisky or rum. Same tiny-word energy, just one ends in sticky fingers and the other ends in someone saying they only wanted a splash.
Usage examples
"Got the tots down for a nap, so I poured myself a tot of rum. Ten minutes later he’s awake and I’ve still got nothing in the glass."
"Granny poured herself a tot of brandy after we put the tots down for the night, said it was medicinal and watched the snooker with her feet up by the heater."
"The tot at the next table at the cafe was throwing chips at the pigeons through the window, his dad pretended not to notice and just kept reading the football scores."
"He’s only a tot, mate, give him a chance to get his wellies on before you march off to the park."
"Go on then, just a tot of whisky in the tea mug and I’ll stop pretending this weather’s character-building."
Where it comes from
Tot is an old English word built around the idea of smallness. The child sense is recorded from the 18th century for a little one or toddler. The drink sense also grew in British English for a small serving of spirits, especially rum, and later became strongly tied to navy and pub talk.