It used to be said that the human tongue perceived flavor in the form of four basic tastes: sweet, sour, salty and bitter. Then a Japanese scientist, Ikeda Kikunae (1864-1936), detected a rich, satisfying taste common to meat, cheese and Japanese dashi (stock) — among other things — which couldn't be placed among the traditional four. He called it umami.
The source of umami, which is sometimes optimistically translated as "savoriness" or "meatiness," is a group of amino acids. Food specialists recognized Ikeda's discovery a long time ago, but the idea has taken much longer to filter through to the general public — not least because of the problem of discussing a taste for which there was no English word.
It strikes me as very peculiar that other languages never developed an expression for this essential flavor.