Two mysterious white thermostat wires in an unfinished wall outlet near the floor -- what?
These wires could be from any low voltage system. Some definite possibilities, besides a thermostat, include:


Doorbell
Security System (aka Burglar Alarm) - each sensor typically uses two wires
Telephone - unlikely because normally telephone wires will be in pairs (or groups of pairs) within a cable rather than individual wires


These may actually be cables containing multiple wires. I couldn't (easily) find an answer for this specific wire - plenty of people selling it but not with very clear descriptions. Strip the white covering off and see what the wires look like inside and post a picture. If there are multiple wires then the colors and/or type of wires may help narrow down the possibilities.

The trick is finding the other end. I would check around any breaker panels, telephone panel (aka Network Interface), security system (if you have one), doorbells (if you have any), etc. Look anywhere that has a lot of wires to see if there is a pair of unused wires/cables that match this pair.