いただきます is the humble form of itadaku (頂く), “to receive.” The 頂 character means the crown of the head — the old gesture was lifting something you’d been given above your head to show respect when accepting it from someone above you. So literally: I humbly receive.

It isn’t “let’s eat,” and it isn’t grace — it’s not addressed to a god. It thanks the whole chain: the plants and animals that died, the people who grew and caught and carried it, whoever cooked. It’s also said when accepting a gift, not just food.