But is not 'parents' or Horim in Hebrew, a modern word only??
as in--
http://dafyomi.shemayisrael.co.il/rhashanah/backgrnd/rh-in-011.htm
*16*) [line 33] "MEDALEG AL HE'HARIM" BI'ZECHUS AVOS - "skipping over the mountains" in the merit of our forefathers [Avraham, Yitzchak, and Yaakov]. This reveals that the "mountains" mentioned in the previously quoted verse refer to the Avos. RABEINU CHANANEL explains that the word "Harim" -- "mountains" -- can be read as "Horim" -- "parents".
rukomoinic, Minneapolis, USA
The Midrash explicitly uses the exegetical approach suggested by Rabbeinu Chananel in Devarim Rabah #1 (on "Rav Lachem Sov Es ha'Har ha'Zeh").
"Horeh" meaning "parent" is not a modern word; it is used in Midrashic literature (e.g. Bereishis Rabah 76:2 - see also Kidushin 82b and Rashi). It is based on the Biblical "Horah" (Iyov 3:2) which means conceived - thus "Horim" are "conceivers."
I hope this makes things more clear.
Best wishes,
Mordecai Kornfeld
Kollel Iyun Hadaf