Origin

The character 駒 combines the radical for horse (馬) on the left with a phonetic component (句) on the right that provides a sound hint for how to pronounce it. The left side immediately signals the character is about horses, while the right component suggests the pronunciation. Over time, the character came to specifically mean a young horse or pony, narrowing the broader concept of horse into a more specific animal category. The combination of a meaningful element (the horse radical) with a sound hint is a common pattern in kanji formation.