That's because a bed was often a big bag with hay inside in the past.

那是因为在过去，床常常是装着干草的大袋子。

youdao

Guests sleep in a thermal sleeping bag on a special bed built of snow and ice, on reindeer skins.

以冰雪做成的特别的床上铺着驯鹿皮，客人们就在上面的加热睡袋里睡觉。

youdao

He stands at the door holding the greasy bag while I wonder if this is the night I'll finish off my spring roll, climb into bed, and have a heart attack in my sleep.

他手里拿着油腻的袋子站在门口，我不禁怀疑这次我吃完春卷爬到床上的之后，我会不会在睡梦中心脏病突发而死去。

youdao

The woman told police that after she had thought the suspect went to sleep in his own bed, she slept in a sleeping bag provided to her by the rally.

WSJ: ObamaCare's Heritage

Seven boxes of ammunition were found after the rampage in a black bag discovered in a dry river bed in Loughner's neighborhood.

CNN: STORY HIGHLIGHTS

The prosecutor said Lewis admitted that he left Planter's body wrapped in plastic on her bed and stashed the child's remains in a plastic bag in a freezer.

WSJ: NY man admits killing woman and her 2-year-old son