I ran across the expression "hell for leather" in the Halberstam book I've been reading, and had to admit I'd never seen it before – I had to look it up.
It apparently means to do something doggedly or recklessly – the latter meaning seems to be under the influence of a different, unrelated expression, "hell bent." The most plausible etymology was that it refers to the effects that an arduous journey had, in the 19th century, on shoes (i.e. "leather"). To take a long, dogged, difficult trip was "hell for leather." Hence the primary meaning of doing something arduous in a dogged fashion. The phrase "hell bent," however, had influenced the meaning of the expression by the beginning of the 20th century, and I think the soldier Halberstam is citing as using the phrase means it more as "to do something recklessly and at great speed."
Having finished the book yesterday, I will say I'm not as disappointed in it as my friend Peter (who gave me the book, I believe, if not quite intentionally). I think ultimately with a modified title it would have been much less disappointing. Halberstam's title is "The Coldest Winter: America and the Korean War". I would only change the subtitle: "The Coldest Winter: How Douglas MacArthur's Mistakes in Korea Led to America's Disaster in Vietnam." That about sums up the book, and with that narrower title, one could be more comfortable with the book's many omissions.
[daily log: walking, km]