Denominative from ro'sh; properly, headship, i.e. (plural for collective) dominion -- principality.
see HEBREW ro'sh
H4761. marashah
[מְרַאֲשׁוֺת] noun [feminine] plural denominative place at the head, head-place; — only suffix מְרַאֲשֹׁתָיו as adverb at his head-place (of one lying down) Genesis 28:11, 18 (E), 1 Samuel 19:13, 16; 1 Kings 19:6; so Qr 1 Samuel 26:7, 11, 16; (Kt מראשׁתו); in 26:12 read ᵐ5 מִמְּרַאֲשֹׁתָיו. We Dr HPS, for מַרְאֲשׁוֺתֵיכֶם שָׁאוּל, מֵרַאֲשֹׁתֵי ᵑ0 Jeremiah 13:18 (head-tires AV:m RV), read מַרְאשֵׁיכֶם, 13:8 (head-tiresAV:m RV), read מֵרָאשֵׁיכֶם from your heads, ᵐ5. ᵑ7 ᵑ6 Gie Buhl CoHpt (compare, already, Thes).