Gehrig had a number of nicknames bestowed on him, for better or worse, since childhood. Weird, accurate, silly, offensive.
In roughly chronological order, here is a list of the post-given-name additions:
"Dumb Dutchman" - by childhood peers because of his German heritage.
"Louie" - by Mom Gehrig, one of two people allowed to call him by a pet name.
"the Babe Ruth of the schoolyards" - by New York press when he was a star high school baseball player.
"Little Heinie" and "Little Dutch Boy" - by residents of Phi Delta Theta fraternity house at Columbia University. Mom Gehrig
worked for the frat house, and Gehrig would usually help her with her chores. Again, these nicknames, or slurs, were
because of his heritage.
"Columbia Lou" - by press during his initial Yankee seasons. He came to the Yankees directly from Columbia University.
"The Crown Prince" (to Ruth's "King") - by press.
"Biscuit Pants" - by players because of his baggy pants over thick legs and a "broad back porch."
"Buster" - by players in the beginning of his career because of his pitch-busting abilities and his young age (20).
"Larrupin' Lou" - by press for his hitting; also used as the name for his barnstorming team he had during off-season.
"The Hard Number" - by fellow AL players, namely pitchers, because of his unrelenting consistency at bat. Technically the
nickname referred to his jersey number (#4).
"Luke" - by wife, Eleanor. Obviously an extension of "Lou." Since it was a pet name, only Eleanor called him that.
"Iron Man of Baseball" or simply "Iron Man" - by press during his prime because of his on-going streak.
"Iron Horse" - by press, fans, historians. The most recognizable and generally accepted-as-official Lou Gehrig nickname.
There was also a legendary locomotive called The Iron Horse.
"Quiet Hero" - by Frank Graham, reporter and Gehrig biographer, after Gehrig's death. It refers to Gehrig's refusal to
be a showboat even though his skill and incredible talent gave him every reason to show off.