Before it was anything else, a rune was a letter, cut into wood, bone, metal or stone by someone who wanted to write something down.
First in the row
Fehu stands first in the Elder Futhark, the twenty-four character row used for the earliest Germanic inscriptions from roughly the second century onward. The row is named after its first six characters, f, u, th, a, r and k, in the same way the alphabet is named after alpha and beta, and Fehu is the f.
What it was cut on
The Elder Futhark corpus is small and consists mostly of short texts on portable objects: brooches, weapon fittings, combs, bracteates and a smaller number of stones. Many inscriptions are a personal name, a maker's formula, or a few words whose reading is disputed. This is not a literature. It is the scattered writing of a period from which almost nothing else survives in the vernacular.
The name and where it comes from
The name Fehu is a reconstruction. The medieval rune poems, written centuries later in Old Norse and Old English, give names for the characters of their own rows, and the Elder Futhark names are projected back from those with the help of comparative reconstruction. The word behind it means livestock and, by extension, movable wealth, and it is the ancestor of the modern English word fee.
Divination
Nothing in the inscriptional record shows runes being used to draw lots in the way modern rune sets are used. That practice is modern, and this atlas records it as such.