From Urdu.

Jhoota: adjective referring to food, drink, or an eating utensil from which someone has already eaten or drunk.

Jhoota in other contexts means liar.

Eating jhoota is often avoided due to concepts of hygiene or social custom, although sharing is common among family/close friends.

It weird that Muslims are very preachy about breaking bread together but also have this concept.

It is of particular importance bc Muslims aren't allowed to eat from utensils that a nonmulim ate.

So its this tainted leftover food which is the precise definition ig.