herdboy; shepherd boy; young ranch hand
Refers to a boy or young man who tends livestock, especially cattle or sheep. The gloss 'cowboy' is possible but can evoke a Western image; in Japanese contexts it is closer to a traditional herding role.
The herdboy led the cattle to the pasture.
その絵には、笛を吹く牧童が描かれている。
The painting depicts a shepherd boy playing a flute.