Letters like wedges (Latin, cuneus, a wedge). These sort of letters occur in old Persian and Babylonian inscriptions. They are sometimes called Arrow-headed characters, and those found at Babylon are called nail-headed. This species of writing is the most ancient of which we have any knowledge; and was first really deciphered by Grotefend in 1802.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Cuneiform Letters from Infoplease: