Acantha: In botany, a prickle; in zoology, a spine or prickly fin. 

Acantha, in Greek mythology, was a beautiful nymph.  Apollo fell in love with her.  She resisted his advances.  While pushing him away, she scratched his face.  In anger, he turned her into a prickly plant. 

These days, the word acantha shows up in the scientific names of spiky plants. 

Acantha comes from the Greek words ἀκή (thorn) and ἄνθος (flower).