from The Century Dictionary.
- noun The oleaginous material obtained from the yolks of hens' eggs. It contains olein and palmitin, with lecithin, cerebrin, neurine, etc., and is used in dressing alum-tanned leather.
Sorry, no etymologies found.
When the world of tempera painters was threatened by the invention of the egg-oil emulsion, which Van Eyck introduced, the same thing probably occurred.