SB 10.58.5
paramasana asinam
krsna krsnam anindita
navodha vridita kiñcic
chanair etyabhyavandata
Translation:
Faultless Draupadi, the Pandavas’ newly married wife, slowly and somewhat timidly approached Lord Krsna, who sat on an exalted seat, and offered Him her obeisances.
Purport:
Srimati Draupadi was so devoted to Krsna that she herself was called Krsna, which is the feminine form of the name, and Arjuna was also called Krsna because of his devotion to the Lord. Similarly, the devotees of the modern Krsna consciousness movement are often called “the Krsnas.” So it appears that the custom of addressing Krsna’s devotees by His name has a long history.