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.
*Based on a 2,000 calorie diet. One serving of dried plums is equivalent in calories to that of about two servings of fruit. Five prunes contain about 30 grams of carbohydrate (equivalent to two slices of bread).