Keerai is spinach and Kootu is a high H2O content, yet thickish, broth generally flavoured with turmeric, cumin, fresh grated coconut, and green chilly among a rotating variety of other toasted spices. Finally flashed with kari leaves and mustard (maybe fenugreek too) in the sheer magic of thalichukottufication (bagaar, in the north).
It is not a snack item. It is serious.
Meenammal: Dai! You eat and go. Rascal.
Kamakshi: (giws one pleading look)...
Bobby (sotto voce): But Kama... they have mutton biriyani at work today!
Meenammal (from the kitchen): Kamakshi, you tell that useless fellow to stay and take lunch at home with us, or else...
Kamakshi (loudly): Bobby, darling, amma has made keerai kootu (followed by flashing eyes types withering look)
Bobby (wordlessly sits down): ...
Meenammal (appearing with cheenchetti of steaming keerai kootu): "Darling" and all donant! Eat now, you wont get this in the canteen anywhere!