An Etymological Dictionary of Astronomy and Astrophysics

A diffraction grating in which the groves are relatively widely spaced and
serves to provide high resolution and dispersion.

Etymology (EN): Echelle, from Fr. échelle “ladder,” , from O.Fr. eschele, from
L. scala “ladder;” → grating.

Etymology (PE): Turi, → grating; nardé, contraction of nardebân “ladder; échelle.”