English
heterozygote
From hetero- + zygote.
Proto-Indo-European *sem- ‘one, whole’
Proto-Indo-European *sḿ̥teros
Proto-Hellenic *hə́teros
Ancient Greek ἕτερος ‘other, another, different’
English hetero-
Proto-Indo-European *yewg- ‘to yoke, harness, join’
…
Proto-Hellenic *dzugón ‘yoke’
Ancient Greek ζῠγόν ‘the yoke of a plow or carriage’
Ancient Greek ζυγόω ‘to yoke or join together’
Ancient Greek ζῠγωτός ‘yoked’
English zygote
The story
Coined by English biologists William Bateson and Edith Rebecca Saunders in 1902, in a paper titled "The facts of heredity in the light of Mendel’s discovery".
Today it means
noun A diploid individual that has different alleles at one or more genetic loci.
Language periods are conventional ranges, not dates for this word.
Etymograph / heterozygote