A shuck is a husk or pod, like a corn husk or nut shell. Its' vernacular, "aw shucks," is like saying garbage or junk. It isn't an abbreviation, so it doesn't stand for anything.
Cowboys loved a colorful phrase! The shucks are the husk of the corn, the part you toss away. Shucks were what cowboys called worthless people or things.
Shucks are the husks of the corn ear. People sometimes say "aw, shucks!" when they're slightly embarrassed. The implication is that they use that word instead of saying some other word starting with S that would not be as polite!
aw shucks
According to Urban Dictionary there are two possible meaning for shucks. The first is euphemism for disappointment and the other is used to express modesty.
aww shucks
Donald Duck
It is basically the equivalent of saying "Darn," "This stinks," or "Dang." I haven't heard anyone use the expression "aw shucks" anymore. They mainly will say one of the examples above or start cursing.
aw shucks Its so bad that it is so good. :)
CSK automotive aka checkers shucks and kragens
Your battery does not stay charged. You can take it to a shucks or napa to have it check free. Ed
Spitting Image Kin Squat Kiss My wrist lam shucks telegraph
There are three proper nouns in the phrase: Sally, Shucks, Seashore.