The strongest line in Japan must be SaiKyo Line.
"Saikyo" means "the strongest" in Japanese, which is the reason why SaiKyo line is stronger than any other line in Japan.
Of course the name of SaiKyo Line isn't from "Saikyo:the strongest"
but from Saitama and Tokyo, which the line conects.
Each of Saitama and Tokyo is made up of two kanjis : Saitama is Sai & Tama,
Tokyo is To & Kyo.
Saitama's Sai and Tokyo's Kyo mint Sai-Kyo.
Naming in this manner is often adopted when it comes to railway's name,
like ToYoko Line, KeiHin Tohoku Line, KeiOh Line, KeiYo Line, KeiSei Line and so on.
What about in U.S.A.?
I wonder if the name of NY-Boston line is the same as an great physicist's.