The Collaborative International Dictionary of English v.0.48:

Red-gum \Red"-gum`\ (-g?m`), n. [OE. reed gounde; AS. re['a]d
   red + gund matter, pus.]
   1. (Med.) An eruption of red pimples upon the face, neck, and
      arms, in early infancy; tooth rash; strophulus. --Good.
      [1913 Webster]

   2. A name of rust on grain. See Rust.
      [1913 Webster] Red-hand