Etymology

From Brennu-Njáls saga, a phrase uttered by Kári Sölmundarson. Consists of ber ‎(“bare”) + er ‎(“is”), from vera ‎(“to be”) + hver ‎(“each, everyone”) + að ‎(“concerning, to”) + baki the dative singular form of bak ‎(“back”) + nema ‎(“unless”) + sér, dative form of sig ‎(“oneself, one”) + bróður, the accusative form of bróðir ‎(“brother”) + eigi, form of eiga ‎(“to own”).

Literally meaning that the "back of each man is bare, unless he has a brother to him".