Can't say for sure but maybe one is an output for connecting an outside TV on the 'patio'.
You did look inside for more than one cable near the television etc. where you would normally connect your receiver. The receiver output would then connect to to the TV. Are you using an external dish where it is logical to connect it to one of those terminals???
Too many other possibilities without more information and investigation on your part!!
Alfa 38 5ver (Florida)