The meaning of Visa

The other day while in the car, ML asked the meaning of the word "visa". Specifically the document that we need to visit another country, not the credit card. Albeit a simple word, I have never thought the real meaning. I actually conjured up an ill-fitting "meaning": VISiting Approval :P

Anyway, I googled a bit and found this:

A visa (short for the Latin carta visa, lit. "the document having been seen") is a document issued by a country giving a certain individual permission to formally request entrance to the country during a given period of time and for certain purposes (see below for caveats and exceptions).