The triangular shaped flaky pastry filled with spicy potato, chicken or lamb filling is a popular snack not only in India but in several countries of the world. Because samosa is so so common in India (you literally get samosa and chai at every other street corner), I always considered it to be a quintessential Indian delicacy.
But only later I read that it has its origin in Middle East and it was introduced to India during the Delhi Sultanate rule. It was later adapted as a vegetarian snack with spicy potato filling in India (which is what is most popular in northern India).