What is "multiple" myeloma?
J. Von Rustizky, a Russian pathologist working in the laboratory of Friedrich von Recklinghausen (1833–1910) in Strassburg in 1873, introduced the term “multiple myeloma.” At autopsy, a 47-year-old patient examined had eight separate tumors of bone marrow, which Von Rustizky called “multiple myelomas,” and he noted that the nucleus of the tumor cells was located in the periphery of the cell membrane — a morphology highly suggestive of plasma cells.


source: Kyle, RA, Steensma, DP (2011) History of multiple myeloma. Recent Results Cancer Res., 183: 3-23

From the same item:


  The most commonly recognized [first documented] case is that of Thomas Alexander McBean, a highly respectable tradesman from London in 1850. Mr. McBean excreted a large amount of protein that was described by Henry Bence Jones in the middle of the 19th century. Jones was a well-known physician and made many contributions to medicine.


The Bence Jones protein is in fact an immunoglobulin light chain. Purified Bence Jones protein were sequenced by FW Putnam, and 
variations between patients were some of the first clues to the existence of the variable regions of immunoglobulin molecules.