gussied up, to get (all)

gussied up, to get (all)

To be dressed or to dress in one’s best clothes. This Americanism from the first half of the twentieth century is of uncertain origin. One theory is that it comes from gusset, a triangular piece of material put into a garment so that it fits better; this word in turn comes from the French gousset and dates from the Middle Ages, when such pieces were put into mail armor so that the knight it enclosed could move better. Because gussets might be considered a bit of fancy dressmaking, the theory holds, one’s best clothes would have more of them than everyday attire.
See also: get, gussied