black spleenwort
noun
Either of two small ferns commonly found on rocks and walls, maidenhair spleenwort, Asplenium trichomanes, and (now more usually) the Eurasian fern A. adiantum-nigrum, which has triangular fronds with a dark base to the stem.
Origin
Late 18th century; earliest use found in Stephen Robson (1741–1779), botanist.