My uncle often caddied for professional golfers when he was young.

caddied 是动词 caddy 的过去式。caddy 指在高尔夫球比赛中为选手携带和递送球杆的人，即"当球童"的意思。这个词来源于苏格兰语，原指"搬运工"，后来专指高尔夫球童。