The term 'Old Icelandic Book' refers to the Edda, a collection of Old Norse poems and stories from Iceland. The Edda was written in the 13th century and is one of the most important sources for understanding Norse mythology and culture. It is divided into two parts: the Poetic Edda and the Prose Edda. The Poetic Edda contains a collection of mythological and heroic poems, while the Prose Edda is a handbook of poetic language and style.