An Etymological Dictionary of Astronomy and Astrophysics

A triangle no two sides of which are equal.

Etymology (EN): From L.L. scalenus, from Gk. skalenos “uneven, unequal, rough,” from skallein “chop, hoe,” related to
skolios “crooked,” from PIE base *(s)qel- “crooked, curved, bent;” → triangle.

Etymology (PE): Sebar, → triangle; nâjur-pahlu “dissimilar sides,” from nâjur “dissimilar, ill-matched” + pahlu “side, flank” (Mid.Pers. pahlug “side, rib,” Av. pərəsu- “rib,” Ossetic fars “side, flank,” cf. Skt. párśu- “rib,” Lith. piršys (pl.) “horse breast”).