Survival of the fittest, and the Japanese word says suited, not strongest: the one that fits its surroundings is the one that lives, and the surroundings decide. The English phrase is Herbert Spencer's, which Darwin borrowed and called more accurate than his own natural selection; the Japanese word was made in the Meiji years in the same rooms as the words for the struggle for existence and natural selection, tried three forms, and kept the one written here, the fit one rather than the fit species or the fittest. It is not 弱肉強食, the strong devouring the weak. Whether you take it as Darwin's phrase or as the Japanese word that says suited is yours.
適者生存 is composed of the words 適者 (read tekisha) meaning "the fit" and 生存 (read seizon) meaning "survive" or "exist".
The English phrase is Herbert Spencer's, coined in 1864 and adopted by Darwin in 1869 as more accurate than his own natural selection; the Japanese word settled in 1883, out of Morse's Tokyo lectures, replacing an 1881 form that made the fit a species.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 適者生存.