'embryo' originates from Greek, specifically the word 'ἔμβρυον' (embruon), where 'en-' meant 'in' and 'bruō' meant 'to swell or grow.'

'ἔμβρυον' transformed into the Latin word 'embryo,' and eventually became the modern English word 'embryo' through Old French.

Initially, it meant 'to swell or grow within,' but over time it evolved into its current meaning of 'an early stage of development.'