All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is nothing wrong with naming a new-born baby-boy with the name Salah. We are not aware that this name is mentioned in the Torah or that it is a biblical name.
It is a common name among Muslims.
The basic principle about names is that they are permissible and not forbidden.
As regards its meaning, Salah is the opposite of corruption.
Among the definitions that are mentioned in dictionaries about its meaning, is righteousness, being free from defect or fault, goodness, correctness, and benevolence.
It was also said that Salah is a proper name for Makkah; Ibn al-Atheer stated this in an-Nihaayah.
For more benefit on naming children with good names, please refer to Fatawa 82724, 87262, 88553 and 87596.
Allah knows best.