'yolkless' is formed from the noun 'yolk' (Old English 'geolca'/'geolc', related to 'geolu' meaning 'yellow') plus the adjective-forming suffix '-less' (Old English 'lēas', meaning 'free from, lacking').

The element 'yolk' comes from Old English words such as 'geolca' and is related to words for 'yellow'; the suffix '-less' comes from Old English 'lēas'. The compound meaning 'without a yolk' arose in Modern English by combining these two elements.

Initially the parts meant 'yellow (yolk)' and 'free from' respectively; together they have long meant 'lacking a yolk' and retain that literal sense in modern usage.