SAP is the Second Audio Program
A lot of TV shows are broadcast in two languages, so TV companies have incorporated SAP control.
I'm betting he somehow found the SAP control on the remote(it may be labeled as something else).
If it is text, there may be a display, or Closed Captioning button to be found somewhere on the remote
We don't have cable TV but noticed the Spanish captioned on the ABC. Went to the menu on our remote control and went to closed captioned and turned it off.
I don't mind the CC however the network puts it in the middle of the screen!!