1560s, to remove (a nut, etc.) from a shell, from shell (n.). The meaning to bombard with shells is first attested 1856. To shell out disburse (1801) is a figurative use from the image of extracting nuts. Related: Shelled; shelling.
There are 14 calories in 1 cup, slices (3 oz) of Nopales (Cactus Leaf), raw. You'd need to walk 4 minutes to burn 14 calories. Visit CalorieKing to see calorie count and nutrient data for all portion sizes.
The wealth of health benefits that come from nopales are mainly attributable to its nutrition and vitamin content, which includes riboflavin, vitamin B6, copper, iron, fiber, vitamin A, vitamin C, vitamin K, calcium, potassium, magnesium, and manganese.