Anglo-Saxon Riddles of the Exeter Book/Annotated/XI. Runes
Runic writing was brought to England from the Continent in the fifth century and ceased to be used after the Danish invasion of 866. The word rūn early took on a sense of mystery—as in The Wanderer iii, gesæt him sundor æt rune (‘sat apart in secret communing’). Cynewulf used runes as a kind of code signature. In the Riddles they serve as a test of knowledge, as much as to say: I give you the clues in this form instead of by ambiguous description.