Ratatoskr

In Norse mythology, Ratatoskr (Old Norse, generally considered to mean "drill-tooth" or "bore-tooth") is a squirrel who runs up and down the world tree Yggdrasil to carry messages between the Veðrfölnir, perched atop Yggdrasil, and the Níðhöggr, who dwells beneath one of the three roots of the tree. Ratatoskr is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson.

The name Ratatoskr contains two elements: rata- and -toskr. The element toskr is generally held to mean "tusk". Guðbrandur Vigfússon theorized that the rati- element means "the traveller". He says that the name of the legendary drill Rati may feature the same term. According to Vigfússon, Ratatoskr means "tusk the traveller" or "the climber tusk."

Sophus Bugge theorized that the name Ratatoskr is a loanword from Old English meaning "Rat-tooth." Bugge's basis hinges on the fact that the -toskr element of the compound does not appear anywhere else in Old Norse. Bugge proposed that the -toskr element is a reformation of the Old English word tūsc (Old Frisian tusk) and, in turn, that the element Rata- represents Old English ræt ("rat").

According to Albert Sturtevant, "[as] far as the element Rata- is concerned, Bugge's hypothesis has no valid foundation in view of the fact that the [Old Norse] word Rata (gen. form of Rati*) is used in Háv[amál] (106, 1) to signify the instrument which Odin employed for boring his way through the rocks in quest of the poet's mead [...]" and that "Rati* must then be considered a native [Old Norse] word meaning "The Borer, Gnawer" [...]".

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