An Etymological Dictionary of Astronomy and Astrophysics

Not occurring very often; not found in large numbers.

Etymology (EN): M.E., from O.Fr. rere “sparse” from L. rarus “thinly sown; not thick; having intervals between.”

Etymology (PE): Perz, in several Iranian languages and dialects “little, few, small, minute part of any thing” (Khonsâri: perz, Qatrâni: perzema,
Birjandi: porzu, Farâmarzâni: pesk, Kurd petik, Tabari: perik “minute quantity, particle”); maybe ultimately from Proto-Ir. *paraka- “small part,” → part.
Kamyâb “rare, difficult to find,” from kam “little, few; deficient, wanting; scarce”
(Mid.Pers. kam “little, small, few,” O.Pers./Av. kamna- “small, few”);

• yâb present stem of yâftan, yâbidan “to find, discover; to obtain, acquire”
  (Mid.Pers. ayâftan, ayâpênitan “to reach, attain;” Manichean Mid.Pers. ‘y’b “to attain;” Parthian, Sogdian (+ *pati-) pty’b “to reach, obtain;” Av. ap- “to reach, overtake,” apayeiti “achieved, reached;” Skt. âp- “to reach, gain,”
  âpnoti “reaches, gains;” Gk. hapto, haptomai “to touch, cling to, adhere to;” L. apiscor “touch, reach;” PIE base *ap- “to take, reach”).