What's the double meaning of "the boy in the striped pajamas"?

When Bruno, who is only nine years old, looks out of his window and sees the concentration camp, he comments that there are people who are wearing "striped pajamas." Bruno is naive and mistakes the Jews' concentration camp uniforms for striped pajamas. The striped pajamas are actually uniforms that the Jewish prisoners at Auschwitz are required to wear.In addition to their striped uniform, they are also required to wear an armband with the Star...

When Bruno, who is only nine years old, looks out of his window and sees the concentration camp, he comments that there are people who are wearing "striped pajamas." Bruno is naive and mistakes the Jews' concentration camp uniforms for striped pajamas. The striped pajamas are actually uniforms that the Jewish prisoners at Auschwitz are required to wear. In addition to their striped uniform, they are also required to wear an armband with the Star of David sewn on it, and a striped cloth hat. The reason the uniforms look like pajamas is because they are made out of thin cloth, which is the same material pajamas are made from. Towards the end of the novel, Bruno comments on how dirty the uniform is that he puts on. This is because the prisoners would have to work and sleep in the same uniforms, and they would be changed approximately every six weeks. Historically, concentration uniforms had personal identification numbers printed on the cloth. There would also be a color-coded, inverted triangle that signified the reason they were imprisoned. In the novel, the Jewish prisoners walked around barefoot. Historically, the prisoners were given either wooden clogs or thin leather shoes with no socks. However, many prisoners were barefoot because of the increasing prisoner population and short supply of shoes.