The Collaborative International Dictionary of English v.0.48:

Minder \Mind"er\, n.
   1. One who minds, tends, or watches something, as a child, a
      machine, or cattle; as, a minder of a loom.
      [1913 Webster]

   2. One to be attended; specif., a pauper child intrusted to
      the care of a private person. [Eng.] --Dickens.
      [1913 Webster]

WordNet (r) 3.0 (2006):

minder
    n 1: someone (usually in totalitarian countries) who is assigned
         to watch over foreign visitors; "I turned around and there,
         a few hundred feet away, was our government minder, Li Wong
         Su, huffing and puffing toward us"
    2: a person who looks after babies (usually in the person's own
       home) while the babys' parents are working [syn:
       babyminder, baby minder, minder]