This is one of the best all around sites that I have found. It is titled “The MacTutor History of Mathematics Archive.”

http://www-history.mcs.st-and.ac.uk/~history/

This is an award-winning site that links to all sorts of mathematics information.

http://archives.math.utk.edu/

Euler circuits were named after Leonhard Euler (pronounced “Oiler”. You might wish to check out this interesting and important person in the history of mathematics.

http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Euler.html

Hamiltonian cycles are named after William Rowan Hamilton:

http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Hamilton.html

Klein bottles (Problem 60) are named after Felix Klein:

http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Klein.html