Damp smell in one room only but no sign of damp!

BlushingRose

Hi all,
Wondering if anyone can help.
We have a house, I'd say a 1950s build, semi-detached and just over a week ago i started noticing a small of damp in one room. The room is a down stairs room with one exterior wall, and that wall is showing no evidence of damp.
We spent a day moving stuff about and having a clear-out to try and find the cause, but nothing is obvious and the smell isn't easy to pin down to one specific area either.
It smells of damp books/old church for want of a better description.

Any ideas about what this could be and how to get rid of it please?

Thanks

paddedjohn

Is it a solid floor in the room or is it a wooden floor? could the smell be coming from below?