Ermine
An ermine was a small Earth mammal that could be described, much like a tribble, as being "nice, soft, and furry." 

After Leonard McCoy made such an assessment with regards to the "practical use" of tribbles in 2268, including the fact that they "make a pleasant sound," Spock retorted that "so would an ermine violin, but I see no advantage in having one." ()

The painting by Leonardo da Vinci, "Lady with an Ermine", featured an ermine. ()

See also 
 Mink
 Weasel

External link 
 

de:Hermelin
Earth animals