It is related to the Latin verb "probare", which has the same meaning.
Here are some examples of English words derived from this root:
* Probe: to investigate or examine thoroughly
* Problem: a question or matter that is difficult to solve
* Probable: likely to happen or be true
* Proof: evidence that establishes the truth of something
* Approve: to formally agree to something
* Probation: a period of time during which someone is tested to see if they are suitable for something
The root "prob" often appears in words related to testing, examination, and verification.