An Etymological Dictionary of Astronomy and Astrophysics

1. A curved structure, normally in the vertical plane, that spans an opening.
   

2. Any overhead curvature resembling an arch.
   → Arches cluster.

Etymology (EN): M.E. arch(e), from O.Fr. arche “arch of a bridge,”
from L. arcus “a bow,” → arc.

Etymology (PE): Taq “arch,” from tâk, contraction of târak, → vertex.