brōsis

This noun is built from the verb for eating, and it keeps that action in view. Sometimes the action is the whole point: Paul says the kingdom of God is not a matter of eating and drinking, he opens the question of food offered to idols by asking about the eating of it, and he tells the Colossians that no one is to sit in judgment on them over what they eat and drink.

From there the word slides easily to what the eating consumes, so that it simply names food. God supplies "bread for food", and in John, Jesus has food to eat that his disciples know nothing about. A close relative, βρῶμα, names the item of food itself and leaves the eating out of view, while τροφή looks at food as nourishment that keeps a body going. πόσις is the drinking half of the pair, and the two words travel together.

John presses the word hardest. Jesus tells the crowd to work not for the food that spoils but for the food that lasts into eternal life, and later calls his own flesh true food. Those sayings work because the plain sense is so ordinary: what a person feeds on is what keeps that person alive, so the real question is what they are living off.

Twice, in the sayings about treasure, the word names not a meal but a ruin. Something eats at what has been laid up, and Jesus sets it beside the moth: the pair stands for everything that quietly consumes wealth from the inside, while thieves attack it from the outside.

What it is that does the eating is argued over. The traditional English rendering is "rust", which suits coins and tools locked in a chest. Others point out that the Greek word says only that something eats, and that it is used elsewhere of a devouring creature, so the phrase may name a second pest alongside the moth: a worm or grub at the stored grain and cloth.

The saying itself is untouched by the argument. Wealth on earth is under slow attack from within, whatever the attacker is called, and that is the contrast Jesus draws with treasure kept in heaven.