Se cailler les miches

Literally: To curdle one's buttocks

Example: “On s'est caillé les miches pendant tout le match au stade.” — We froze our butts off through the whole game at the stadium.

English equivalent: To freeze one's butt off

Origin: Se cailler turns up in Céline in the 1930s: cailler is what milk does as it cools and sets, so the picture is blood thickening in the veins until it will not move. Miches for buttocks comes from the split round loaf and dates from late 19th-century argot, helped by an earlier use of the same word for the moon. The variant les meules is mid-20th century and less confidently explained, probably from the rounded top of a haystack.