The lowest stringed instrument that is typically played in orchestras is sometimes termed a "double bass". Is there a corresponding "single bass"?

Naively, one might think that it would be the cello, but I was under the impression that the cello was a "tenor" instrument, rather than a "bass" one. Then there's the whole stringed instrument family issue (violin vs. viola da gamba vs. ...), which may complicate what a "true" single bass is.

Is there such a thing as a "single bass", and does it (roughly) correspond to any instrument in current widespread use?