The yolk is the yellow part of a bird's egg, so it's not too surprising that the words yolk and yellow share a common ancestry. Linguists tell us that yellow ultimately traces back to the Proto-Indo-European root ghel-, which meant “yellowish” and was used to form the names of colors that fall in the range of yellow to yellowish green. When Old English inherited the root—probably, say linguists, via the Proto-Germanic cognate gelwaz—it became geolu (sometimes spelled geolo or geolwe) and meant simply “yellow,” and from this Old English speakers derived the word geolca (sometimes spelled geoloca or geolelca), the meaning of which was literally “the yellow part,” and used it as the designation for an egg yolk. Sometime during either the eleventh or the twelfth century—linguists and etymologists don't all seem to agree on the chronology here—the spelling for geolu changed to yelowe (or sometimes yelwe) and geolca became yelke. At the end of the fourteenth century, yelowe was finally transformed into the yellow with which we contemporary English speakers are all familiar, but at the same time, yelke received only a minor facelift and became yolke. The form yolk didn't make its first appearance at breakfast tables until the early fifteenth century.
©2022 Michael R. Gates
