colt

Colt comes from Middle English colt, from Old English colt, tracing back to Proto-Germanic *kultaz, meaning something plump or thick-shaped, like a stump or bulb. That in turn comes from Proto-Indo-European *gelt-, meaning a round shape or a child in the womb, rooted further in *gel-, 'to ball up, amass.'

The word began as a general idea of roundness or plumpness — a bulb, a stump, a swelling shape — and narrowed over time to name a specific plump, young creature: a young horse.

Colt shares its deep root with the word child, both descending from the same Proto-Indo-European idea of something round or unborn taking shape.