text: As you suggest, it was used in Shakespeare's Julius Caesar.  It is used to refer to a time where people were younger and far more carefree.  It always reminded me of the deliciousness of the early spring crop of vegetables in Italy, especially.  Each vegetable is so sweet and delicious that any melange seemed like a banquet and they practically required no seasoning, perhaps just a bit of steam and some cold pressed olive oil.  Hence I see salad days as that which is youthful, fresh, filled with flavor and the innocence by which youth will always be oblivious of the hardships and heavy responsibilities yet to come.