The Collaborative International Dictionary of English v.0.48:

Scatter-brained \Scat"ter-brained`\, a.
   Giddy; thoughtless.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shatter-brained \Shat"ter-brained`\, Shatter-pated
\Shat"ter-pat`ed\, a.
   Disordered or wandering in intellect; hence, heedless; wild;
   similar to scatter-brained. --J. Goodman.
   [1913 Webster +PJC]