When I was young, the milkmen left glass bottles of fresh milk at our doorstep every morning.

milkmen 是 milkman 的复数形式，由 milk（牛奶）和 man（人）组成的复合词，字面意思是"牛奶人"，指"送奶工"或"牛奶配送员"。这种职业在以前很常见，负责挨家挨户配送新鲜牛奶。