|Asplenium scolopendrium, I think.|
A cluster of spores makes up a sorus, from the ancient Greek for "pile, heap". In the hart's-tongue, the sori are long rows; in our common native ferns, they're round dots. These long sori reminded somebody of a centipede, so the fern was named, in Latin, for a centipede: "scolopendrium".
(They look more like caterpillars to me, but according to the naming conventions, the first person to describe a plant or critter gets to name it.)
|Here's the whole fern. And the fronds are supposed to look like deer's tongues. With centipedes on the underside.|
The imagination boggles.