The Stars and the Cookie Jar

There's very little to get. Whomever you ask, the basic answer you get is that it's too easy to mistake kitniyyot with grains, so we avoid them in order to create a proper fence around the Torah.

(Rabbi Richard Israel z"l liked to inform people that not all legumes are kitniyyot and not all kitniyyot are legumes. I just read his take on the subject. Seems that a legume is any member of the family Fabaceae. Fabaceae are distinguished by the tendency of their roots to release nitrogen into the soil.)