I learned from a Japanese friend that ふむふむ could be translated like "oh, I got it", "I see", "I know", or "ok". It could be also in this form: ふむふむ なるほど But, my sister lived in Japan for 5 years, and ...
I am at present rigorously studying 擬音語／擬態語 (an entire world of its own!). The definition my book has for ぼちぼち (also ぼつぼつ) is: 1. Gradually; slowly but steadily 2. Used to describe something that is ...
With many 擬音語 (ぎおんご, onomatopoeia) and 擬態語 (ぎたいご, mimetic words) there is a double form, where the word is repeated, and a form with っと at the end. For example: きらきら -> きらっと (sparkling) ぴかぴか -> ...