yolk

Etymology

From Middle English yolke, yelke, ȝolke, ȝelke, from Old English ġeolca, ġeoloca, ġioleca (“the yellow part, yolk”), from ġeolu (“yellow”). Doublet of gowk (“apple core”).

noun

1. The yellow, spherical part of an egg that is surrounded by the white albumen, and serves as nutriment for the growing young.
   To make meringue, you have to separate the white from the yolk.
2. The grease in a sheep's fleece; lanolin.
   Wool-growers appear to entertain different opinions in regard to the effect which yolk has on the value of the fleece. Some seem to suppose that the aggregate amount which they receive for their wool is increased from the greater weight which it possesses by being charged with this substance[…] 1846, The Cultivator, page 270