Equisetum Hyemale

Of course I know it’s called horse tail fern.
But why “horse tail,” and why, for that matter, “fern”?
It doesn’t look like a horse’s anything, so why equus?
and I don’t think “fern” when I see it.

What I do think when I see it is how fascinating,
how utterly outrageously marvelous, how neat
that evolution comes to this and moves on eventually
to slightly more complex living things like me.