noun, plural pso·ai [soh-ahy] /ˈsoʊ aɪ/, pso·ae [soh-ee] /ˈsoʊ i/. Anatomy.
either of two muscles, one on each side of the loin, extending internally from the sides of the spinal column to the upper end of the femur, which assist in flexing and rotating the thigh and flexing the trunk on the pelvis.
Origin of psoas
1675–85; < New Latin < Greek psóās, accusative plural (taken as nominative singular) of psóa a muscle of the loins
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
either of two muscles of the loins that aid in flexing and rotating the thigh
Word Origin for psoas
C17: from New Latin, from Greek psoai (pl)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
1680s, from Greek psoa (plural psoai) "muscles of the loins." Related: Psoitis.
Gk. [psoas], the gen. of the feminine noun [psoa], was mistaken by the French anatomist Jean Riolan (1577-1657) for the nom. of a (nonexistent) masculine noun. It was he who introduced this erroneous form into anatomy." [Klein]
Online Etymology Dictionary, © 2010 Douglas Harper