Wordorigins.org

The meaning of this odd phrase is to travel fast and hard in a seemingly purposeless direction. The metaphor behind the phrase is obscure. Don’t confuse this phrase with hell for leather, which is a different phrase entirely—although the use of leather may come from confusion between the two. Variants of the phrase include hell-bent for election, breakfast, or Georgia.

Hell-bent, meaning recklessly determined or willing to achieve something at any cost, dates to the early 18th century. From Ebenezer Cooke’s The Maryland Muse of 1731:

Ab-origines in Arms...did then resort, In Haste to Susquehanna Fort, Hell bent on Thoughts of Massacree.¹