Literal translation
to be covered up like Saint George
Meaning
to be bundled up in many warm layers
Explanation
This phrase means 'to be bundled up in many warm layers at once'. The literal image evokes Saint George, the figure from Christian tradition depicted in knightly armor for his battle against the dragon, covered head to toe in heavy, complete equipment that leaves no part of the body exposed. Applying this image to someone who has put on several layers of clothing to guard against the cold amounts to comparing this excess of layers to a suit of armor, with a touch of comic exaggeration at an outfit judged disproportionate to the actual cold. The verb meaning to cover, to plug, to hide by covering, suits well this idea of a body entirely wrapped up, with no part left visible or exposed to the cold. The register is familiar and affectionately teasing, often used about a child or a cold-sensitive person found overdressed for the season, but without real reproach, the remark remaining the kind of good-natured teasing typical of family relationships.