An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A fissile rock composed mostly of layers of clay-like, fine-grained → sediments. Shale is the most frequently occurring → sedimentary rock.

Probably from obsolete or dialect shale "scale, shell," from M.E., from O.E. scealu, → rock.

Ardavâl "shale," in the dialectal Mod.Pers. of Golpâyegân, Arâk, Xonsâr, etc.