San in this phrase is the obligatory honorific that translates simply as “Mr.” or “Ms.” Nobori refers to heading toward the capital of Japan. With the addition of the honorific prefix o-, the phrase becomes a satirical reference to the stereotypical lack of sophistication of someone who has come from the “sticks”.
A: Kondo nyuusha shite kita Hara-san ne, chihoo no sanson kara jookyoo shite kita n da tte.
B: Aa, sore de na no ne. Ikanimo onobori-san tte kakkoo shiteru no wa.
A: You know the new employee, Ms. Hara? I hear she came to Tokyo from a small mountain village in the country.
B: Oh, that explains it. She certainly dresses like a country bumpkin.