Vaal'inisia is a faery word meaning the wisdom of the grass. It is the wisdom that tells the grass to bend before the wind and not to stand tall in the face of it. The wisdom to endure the storm rather than fight it. The oak has the strength to stand proud and tall, but falls before the wind. The grass humbles itself by bending it's head to the round before the wind, but it never falls.
In the faery language it is an ordinary word, there is no magic in it.