 Human settlement of the island dates from circa 3000 BC and there are remains of several Neolithic burial chambers known as ' heel @-@ shaped <unk> ' . Little is known of the pre @-@ Celtic and Celtic eras , but when the Norse arrived it is likely they found a religious settlement as the name of the island derives from <unk> <unk> meaning " Big island of the <unk> " ( Celtic monks ) , in distinction to Papa Little some 12 kilometres ( 7 @.@ 5 mi ) to the west . 
