Ogham

Ogham is an ancient Irish alphabet, known from stone inscriptions dating mostly from the 4th to the 6th centuries. It has twenty main letters, made of strokes set on either side of a stem line and arranged in four groups of five; additional letters were added later. Medieval treatises link many of the letters to trees, hence the name “tree alphabet”. Its present-day use for divination, on sticks or tablets, is a modern reconstruction inspired by these associations.