"grounded", which is the US usage, derives from the phrase "tied to earth ground". This derived from the fact that an "earth ground" is literally connected to

"grounded", which is the US usage, derives from the phrase "tied to earth ground". This derived from the fact that an "earth ground" is literally connected to "the ground" ("ground" as in "the surface of the Earth" [1]) because an "earth ground" is a six foot copper pole sunk underground to which the "ground" buss bar in an electrical distribution panel is tied. So in the US, it seems we shortened "tied to earth ground" to "grounded" for common usage while in the UK the shortened version became "earthed" [2]. [1] https://www.dictionary.com/browse/ground https://www.dictionary.com/browse/ground - noun definition #1 or #2 [2] https://dictionary.cambridge.org/us/dictionary/english/earthed https://dictionary.cambridge.org/us/dictionary/english/earth...