'egg-yolk' is a compound of the words 'egg' and 'yolk'. 'egg' originates from Old English 'æg' (from Proto-Germanic '*ajja'), meaning 'egg'. 'yolk' originates from Old English 'ġeolca' (Middle English 'yolke'), from Proto-Germanic '*gailkaz', where the root meant 'yellow'.

'yolk' changed from Old English 'ġeolca' to Middle English 'yolke' and eventually the modern English 'yolk'; later it combined with 'egg' to form the compound 'egg-yolk' (also written 'egg yolk').

Initially, the element 'yolk' emphasized the color 'yellow' (originally meaning 'yellowish part'); over time it came to mean specifically the yellow part of an egg, which is the current meaning of 'egg-yolk'.