In Greek mythology, sirens (singular: Seirḗn; plural: Seirênes) are humanlike beings with alluring voices; they appear in a scene in the Odyssey in which Odysseus saves his crew's lives. Roman poets place them on some small islands called Sirenum scopuli. In some later, rationalized traditions, the literal geography of the "flowery" island of Anthemoessa, or Anthemusa, is fixed: sometimes on Cape Pelorum and at others in the islands known as the Sirenuse, near Paestum, or in Capreae. All such locations were surrounded by cliffs and rocks. Sirens continued to be used as a symbol for the dangerous temptation embodied by women regularly throughout Christian art of the medieval era. The etymology of the name is contested. Robert S. P. Beekes has suggested a Pre-Greek origin. Others connect the name to σειρά (seirá, "rope, cord") and εἴρω (eírō, "to tie, join, fasten"), resulting in the meaning "binder, entangler", i.e. one who binds or entangles through magic song. This could be connected to the famous scene of Odysseus being bound to the mast of his ship, in order to resist their song. Sirens were later often used as a synonym for mermaids, and portrayed with upper human bodies and fish tails. This combination became iconic in the medieval period. The circumstances leading to the commingling involve the treatment of sirens in the medieval Physiologus and bestiaries, both iconographically, as well as textually in translations from Latin to vulgar languages, as described below. The sirens of Greek mythology first appeared in Homer's Odyssey, where Homer did not provide any physical descriptions, and their visual appearance was left to the readers' imagination. It was Apollonius of Rhodes in Argonautica (3rd century BC) who described the sirens in writing as part woman and part bird. By the 7th century BC, sirens were regularly depicted in art as human-headed birds. They may have been influenced by the ba-bird of Egyptian religion. In early Greek art, the sirens were generally represented as large birds with women's heads, bird feathers and scaly feet.