On this particular occasion, he woke up after a nine-day drunk hanging upside down in Yggdrasil, the world tree. Right then and there he ripped off a branch and carved a pipe and nicknamed it his spear, because after filling the pipe, he missed his mouth completely and poked out an eye. He was so embarrassed that he made up this story about plucking out his eye on purpose—for some drink or another—so he could write poetry. As Odin said afterward (that is, his coverup),

Veit eg að eg hékk
vindga meiði á
nætur allar níu,
geiri undaður
og gefinn Óðni,
sjálfur sjálfum mér,
á þeim meiði
er mann-gi veit
hvers hann af rótum renn.

From "Hovamol," The Poetic Edda,
courtesy of Garðar Jóhann

I ween that I hung
    on the windy tree,
    Hung there for nights full nine;
With the spear
    I was wounded, and offered I was
    To Odin, myself to myself,
On the tree that none
    may ever know
    What root beneath it runs.

From "Hovamol," The Poetic Edda,
trans. by Henry Bellows