Where does “ראָש־השנה” come from?

ראָש־השנה (Yiddish) comes from Hebrew רֹאשׁ הַשָּׁנָה — beginning of the new year.

Ancestry of “ראָש־השנה”, step by step

Step	Language	Word	Meaning
1	Hebrew	רֹאשׁ הַשָּׁנָה	beginning of the new year

ראָש־השנה — Etymology, Origin & Word History | Etymology Explorer