Suelo is Spanish for “floor” although it is not too common (piso is the more common word). But, very common is subsuelo — the sub-floor, that is: the basement.
This is, unexpectedly, related to a few English words.
Suelo comes from the Latin solum, meaning “ground.”
From solum, we get two English words:
First, soil — yes, the soil is what is on the ground below you!
Second, sole — as in the sole of your shoe. This, too, is below you as you walk.
In both, we clearly see the s‑l root staying consistent.