In English, we have the expression ‘cool as a cucumber’. It was first recorded in a poem by John Gay in 1732. The Swedish version of this is ‘cool/calm as a bowl of fermented milk’, or ‘lugn som en filbunke’ in Swedish.
What, you might be asking, is a filbunke? Well, according to the dictionary it is ‘milk that has fermented, unstirred, in small bowls. Has a pudding-like consistency. Traditionally made in small bowls from (unpasteurized and unhomogenized) raw milk, which normally contains some cream. The cream forms a yellowish layer of sour cream on top. Comes unflavoured and flavoured.’
We don’t have an equivalent dish in English as far as I know.
Although the dish has been around since the 1600’s, the expression ‘cool as a filbunke’ entered the Swedish language in 1845. Playwright Johan Jolin wrote in his play ‘A Comedy’ – ‘I’m cool, cool as a filbunke’. It was met with much hilarity. I guess he thought there was something chilled out about a bowl of fermented milk.