Boro (ぼろ) is derived from boroboro, meaning something tattered or repaired.

And Boros are just that: textiles that have been patched together for generations. 

Boro were blankets and clothing worn by the peasant farming classes in the Northern regions of Japan, who mended their garments with spare fabric scraps out of economic necessity. Cotton could not be cultivated in these cold areas, making hemp more available. Boro are woven together of these fabrics.

Today Boro textiles are considered works of art, representing years of folk crafts.