Compound of 子 (young, small) + 馬 (horse). Follows the common pattern of 子 + animal to indicate a young animal.
Related words
- 子犬 — puppy
- 子猫 — kitten
- 子牛 — calf
- 親馬 — parent horse
- 母馬 — mare (mother horse)
Cultural note
Horses have a long history in Japan, particularly in 北海道 where horse breeding is still a major industry. The 日高 region is famous for thoroughbred breeding.