Friend to the rock

Anybody ever hear about a sayng "friend to the rock" or "good to the rock"? It'd meaning really good friend or really good people.

I've never heard the saying, but it sounds as though "rock" in this saying would be the equivalent of "rock-bottom" in some of its uses. One of the meanings given for "rock-bottom" by the OED is "fundamental, firmly grounded, honest, sound." One of their examples is "1866 Oregon State Jrnl. 24 Nov. 2/2 A sound democrat, or 'rock bottom', never shrinks from the requirements of his master."

I also think "friend to the bedrock" or "good to the bedrock" is also a little clearer than just "friend to the rock."
SS