What does "sine" mean?
According to Textbook of metabolism and metabolic disorders (1964): 


  The ribosides derived from purines have the suffix -osine; those from pyrimidines, the suffix -idine. The corresponding deoxyribosides, with the exception of thymidine, do not have any such simple designation. Occasionally, instead of, for example, guanine-deoxyriboside, the term deoxy-guanosine is used. 


Beyond the more common adenosine and guanosine, there are also: 

inosine  and  

xanthosine