An Etymological Dictionary of Astronomy and Astrophysics

1. A solid disk or a rigid circular ring arranged to turn around an axle passed through the center.
   

2. Anything like a wheel in shape or function.

Etymology (EN): M.E. whel(e), O.E. hweol, hweogol,
from PIE *k(w)e-k(w)lo- “wheel, circle;” cf. Gk. kyklos “circle, wheel;” L.L. cyclus; Mod.Pers. carx “wheel;”
Av. caxra- “wheel;” Skt. cakra- “wheel, circle;” Rus. koleso “wheel.”

Etymology (PE): Carx “wheel,” akin to wheel, as above.