I came across the phrase, “Let’em up easy,” in the following sentence in the section of “1864 Reelection” of “Abraham Lincoln” in Wikipedia, the free encyclopedia:
"Reconstruction began during the war, as Lincoln and his associates anticipated questions of how to reintegrate the conquered southern states, and how to determine the fates of Confederate leaders and freed slaves. Shortly after Lee's surrender, a general had asked Lincoln how the defeated Confederates should be treated, and Lincoln replied, "Let 'em up easy, General.”---Determined to find a course that would reunite the nation and not alienate the South, Lincoln urged that speedy elections under generous terms be held throughout the war."
As I was unable to get an idea of "Let 'em up easy,” I consulted English dictionaries at hand. None of them registers “let sb / stg up easy,” nor did Google Ngram show the incidence of the phrase since 1840, more than a quarter century earlier than the President used it.
Is this famous line, “Let’em up easy,” inscribed in the history, a just one-off phrase used by President Lincoln, or then-current-but-now-an-obsolete phrase?