What's the meaning of "blue blood"?

x��P�N�@���mlLX;��z�
&�a��R`����UV4�X�d�[�~�F^���l"��S�9�{�U}��Ab��p0xQBm`�t7Ġ����U��t����'�_��tR�DU��Y͊�����OU�>��6P��i��=��E�����@0�p��iI�XD>I��%�:zl篣T�������3�����( �� �(`!5���1�=�mV̲b�ԟ7U [���_V��tՋ�i������*����zQ%��A1j.����G*~��Kh�[).���){�`�_a�݌