Too broad as MO question. I think there is a consensus about the history of the use of letters in mathematics. Apart from that, each single notation has its own history. Which of these have you in mind?

There is a paper entitled "Top mathematicians of the world!" in EMS Newsletter (Dec 2014, pp. 32-34): ems-ph.org/journals/newsletter/pdf/2014-12-94.pdf. It is not exactly what you are looking for, but it discusses the problem of evaluating researchers and research in mathematics.

Have a look at this ted.com/talks/terry_moore_why_is_x_the_unknown?language=en

@LeeMosher Please see my comment above

@René Indeed, my conclusion was not just based on a few paragraphs I mentioned above. It was based on my previous reading of Khayyam. Tying algebra to geometry costed him and progress of mathematics a lot (about five hundred years for the latter).

I remember (though not sure), Polya, somewhere in his book "Mathematical discovery", claims that Pascal triangle is deserved to be called as such since Pascal did many things with it including using induction for the first time. Of course, it is different from recognizing it as the foundation of number theory. But, I would be very happy to have your comment on the origin of the idea of induction.

@MichaelBächtold Thank you for the comment. Indeed, when I used depth contours in the class I realized why height contours are better as a teaching tool. With the height one you can automatically talk above walking on the surface, something that is not working with depth contours and swimming

The passage is beautiful and enlightening. Many thanks :)

@GerryMyerson Though I am not sure about the question per se, most of the answers given so far are not a million miles away from the ones could be given to your question; maybe, just 1 mile