This practice stems from a Carpatho-Rusyn belief that if birds or other small animals got ahold of shorn hair and wove it into their nests, the person from whom the hair came would suffer from headache or even become mentally confused.
In older times, this belief was more detailed. In the western Carpathians it seems to have been birds presented the greatest risk of collecting the hair and weaving it into their nests. In the more easterly areas of the Carpathians it seems to have mice that presented the greatest danger in this respect. In its heyday this superstition included such details as the belief that the headache would be continual or last as long as the nest remained.
This superstition is evidently very old, most likely pre-Christian. Historical material shows that this superstition has occurred in England, Germany and Lithuania. Most likely it has occurred all over Europe.
On the Ukrainian countryside this superstition is still well-known and, although is no longer believed, belief is sufficiently recent that burning is still almost universally considered to be the proper way to dispose of hair.