Same entry in the Synagoge and in Photius, Lexicon pi768 Theodoridis, similarly already in Hesychius pi1868. Other editors (though not Adler) capitalize the headword. Unattested outside lexicography (and ignored by LSJ), it is presumably connected with the verb illustrated in pi 1299, q.v.; so perhaps constrictOR, rather than constrictED.
Theodoridis also notes the connection drawn by Schmidt (on Hesychius) with the D scholia on the portentous serpent in Homer, Iliad 2.308: 'Porphyrios in the Investigations says that its name was Sthenios'.