Wikipedia says it best:
“A person (usually a child) who cannot sleep due to worrying can express their worries to a doll and place it under their pillow before going to sleep. Some medical centers use them in conjunction with treatment for disease in children. According to folklore, the doll is thought to worry in the person’s place, thereby permitting the person to sleep peacefully. The person will wake up without their worries, which have been taken away by the dolls during the night.”
The doll is tough as old shoe leather. Literally. Therefore, she’s extremely durable and able to handle extra heavy-duty anxieties She’s suspended by thread.
Here are a few more: