U.S.
Grounded with respect to keeping kids confined is an extension of the application of the electrical term, electrically in contact with the ground (1884). "Earthed" is an older term for electrically grounded, but I haven't heard it within memory (seen in books).

Two time, seven time, etc., could be newspaper writers' coinage (always striving for emphasis and/or simplification, not always successfully); in speech twice or seven times are still commonly heard.

I think we all tend to pick up usages we hear on the TV or read in the paper.