The Collaborative International Dictionary of English v.0.48:

Ichthyol \Ich"thy*ol\, n. [Gr. 'ichqy`s, -y`os, a fish + (prob.)
   L. oleum oil; but cf. Ichthyolite.] (Chem.)
   An oily substance prepared by the dry distillation of a
   bituminous mineral containing fossil fishes. It is used in
   medicine as a remedy in some forms of skin diseases.
   [Webster 1913 Suppl.]