V-structure

In graphical models, a v-structure is a set of three nodes in a graph such that there are two converging arrows and the tails of the arrows are not connected by an arrow. For example, $X\to Z\leftarrow Y$ is a v-structure.

The middle node in a v-structure is called a collider. (?)

Some authors seem to distinguish between a v-structure and an immoral v-structure. In this case, "v-structure" seems to only mean that there is a collision, and the "immoral" means the parents are not directly connected.

Terminology

why is this thing called a v-structure? because it looks like a letter V if the two parents are drawn above the common child?