An Etymological Dictionary of Astronomy and Astrophysics

1. General: Any thin, flat, circular plate or object.
   
2. Math.: The domain bounded by a circle.
   
3. Astro.: A thin, flattened material structure encompassing a central object, such as a star or a galactic nuclear region. → accretion disk;
   → circumnuclear disk; → circumstellar disk; → galactic disk.
   
   Computers: Any of several types of material support on which data can be encoded.

Etymology (EN): From L. discus “quoit, discus, disk,” from Gk. diskos, from dikein “to throw.” → dish.

Etymology (PE): Gerdé, from Mid.Pers. girdag “disk, round,” from gird/girt “round, all around,” Proto-Iranian *gart- “to twist, to wreathe,” cf. Skt krt “to twist threads, spin; to wind; to surround;” kata-
“a twist of straw,” Pali kata- “ring, bracelet,” Gk. kartalos “a kind of basket,” kyrtos “curved;” disk loanword from Fr.