Change accumulated across generations, keeping what works. Evolution has direction without having intent.
Latin evolutio, from evolvere (to unroll), ex- (out) plus volvere (to roll); a gradual unrolling, later borrowed to name change across generations.
Its root is a scroll being unrolled, not a plan being written: evolvere named a gradual unrolling of something already there in full. What survives generation after generation was, in that image, never designed, only slowly uncovered.