Oh man, I was so excited when The Word Detective began to verify my guess...and then the OED knocked it down:
"Gussied up" is a horse of a different color, however, and I think its slightly sarcastic tone is just right for describing someone dressed to the nines. "Gussied up" is usually described as a native Americanism dating to the early 20th century. The "gussy," it is theorized, was actually a "gusset," a triangular piece of fabric sewn into a garment to make it fit better. Gussets were, in those days, typical of fancy clothes and, by extension, a fitting symbol of sartorial frippery.

The Oxford English Dictionary, however, proposes a different, and I think much more likely, origin of "gussied up." It turns out that "gussie" -- a diminutive of the name "Augustus" -- is Australian slang for an effeminate man, dating back to the early 1900's. It's easy to imagine a rich young dandy named "Gussie" incurring the contempt of turn-of-the-century Australians, so I vote for this theory.


Here's what he says about grass:
My original theory was that the root of "grass" meaning "informer" or "traitor" is the expression "snake in the grass," which since the time of Virgil has been a metaphor for a deceitful or treacherous person.

Other authorities, however, trace "grass" to the rhyming slang term "grasshopper." Rhyming slang, common among the Cockneys of London as well as the working classes of Britain and Australia in general, uses a system of rhymes to disguise the words actually meant. In this case, "grasshopper" rhymes with and stands for either (opinions vary here) "copper" (as in police officer) or "shopper" (one who "shops," or sells, information to the police).

Lending credence to the "grasshopper" theory is the fact that while the earliest use of "grass" in print can only be traced back to 1932, an example of "grasshopper" is found as of 1893. If "grass" had come from "snake in the grass," it probably would have shown up much earlier, but as is it appears to have been a simple abbreviation of the already existing "grasshopper."

There has, incidentally, been a further development on the "grass" front in Britain in the last several decades -- the emergence of the "supergrass." These "superinformers" are high-level criminals whose revelations, comparable to those of recent American underworld turncoats, have shaken up major criminal syndicates in Britain.