News to me that it comes from Greek verb meaning to strangle. The circular muscle so
socially indispensible at external lower termination of intestinal tract is called a
sphincter. So the Sphinx was said to kill victims by strangulation.
"sphinx - c.1421, from L. Sphinx, from Gk. Sphinx, lit." the
strangler," a back-formation from sphingein "to squeeze,
bind." Monster, having a lion's (winged) body and a
woman's head, that waylaid travellers around Thebes and
devoured those who could not answer its questions; slain by
Oedipus. The proper plural would be sphinges. "