A stockpot is the big deep pot you make stock in — stock being the tasty water you get from slowly boiling bones, meat, or vegetables, which then goes into soup and sauces. The shape has a reason: it is tall rather than wide, so the water sits deep over the bones and does not boil away too fast during the long, slow cooking. Because it is the biggest pot in most kitchens, people also use it for anything large — boiling noodles for a crowd, making jam, cooking a whole chicken. A cook may say 'put it in the stockpot' meaning the scraps go in to make stock, so the word can stand for the stock-making itself. In old kitchens a stockpot sat on the stove all day and never really emptied; every day's bones and vegetable ends went in. That picture gives the word a warm, thrifty feeling, and you sometimes hear people use it that way about ideas — a place where odd leftover things go and something useful comes out.