Investigate someone thoroughly, especially in order to ensure that they are suitable for a
job requiring secrecy,
loyalty, or trustworthiness.
Derives from late 14th century
Norway where you would investigate and check if a visitor was a vette (a supernatural being or troll) before letting them into your home.
The origin of the word is Proto-Germanic *wihti and is related to the german word "Wicht" and english "wight" and Old Norse ; «vǣt(t)r».