Honey
Out of this minhag later developed another custom (most likely in the 15th century) to dip the challah in honey.
יהי רצון מלפניך ה' אלקינו שתחדש,ואלקי אבותינו עלינו שנה טובה ומתוקה
Some also say a separate yehi ratzon on fish, a custom attributed to the Avudraham.
Head
The mekor for using honey on Rosh Hashanah dates back to the time period of the Geonim and is based on a pasuk in sefer Nechemiah (8:10) in which Ezra and Nechemiah told the Jewish people not to be sad on Rosh Hashanah and exhorted them to enjoy rich foods and sweet drinks. The Machzor Vitry— authored by a talmid of Rashi, Rabbeinu Simchah ben Shmuel of Vitry, and completed in the year 1208 — mentions that for this reason the Jews of Northern France developed the minhag of eating red apples on Rosh Hashanah. Only later, during the Middle Ages, did Ashkenazi Jews combine the minhag of consuming honey and eating apples by dipping the apple in honey, as is mentioned in the Tur.
Fish
יהי רצון מלפני ,אבינו שבשמים שנפרה ונרבה כדגים
The minhag of eating a sheep’s head on Rosh Hashanah dates back to the time period of the Geonim and is also mentioned in the Machzor Vitry as being practiced by the Jews of Southern France. In 14th-century Spain, the Avudraham wrote that those who find it difficult to purchase a ram’s head should eat a fish’s head, and thus the minhag of eating fish and eating a head were combined.
שנהיה,יהי רצון מלפני אבינו שבשמים לראש ולא לזנב September 18, 2017 / THE MONSEY VIEW / 123 www.themonseyview.com / 845.600.8484