An Etymological Dictionary of Astronomy and Astrophysics

Same as → quadrangle.

Etymology (EN): From Gk. tetragonon, from → tetra- + -gon “angled, angular,” from gonia “angle,”
related to gony “knee;” L. genu “knee;” Mod.Pers. zânu “knee;” Av. žnav-, žnu- “knee;” Skt. janu-; PIE base *g(e)neu-.

Etymology (PE): Cahârguš “four-cornered,” from cahâr, câr “four,” cognate with L. quattuor, → four,

• gušé, guš “corner, angle;” Mid.Pers. gôšak “corner.”