schwedische Gardinen

Etymology
lit. 'Swedish curtains'. The idiom was borrowed from the cant called Gaunersprache (≈ thieves’ argot). The word  refers in an ironic /humorous way to the bars on the window in a prison cell. The qualifier  alludes either to the material of the bars, formerly often Swedish steel, considered as extraordinary robust, or perhaps to the atrocities committed by the Swedish during the Thirty Years’ War.

Noun

 * 1)  bars jail, prison, imprisonment

Usage notes

 * This idiom predominantly takes the preposition.