The book is devoted to the description of such a little-studied phenomenon of medieval Russian culture as multiple names. How can the same person accumulate three in a lifetime, four or even five personal names, whether they were used all together or alternately, what was the functional status of each name, what were the rules for choosing names and did these rules change over time? All these and some other questions are discussed here in connection with one of the most mysterious Old Russian documents - the will of the Grand Duke of Moscow Semyon Ivanovich Gordy, drawn up in the plague-ridden capital.