"A Hamiltonian path,
also called a Hamilton path,
is a path between two vertices of a graph that visits each vertex exactly once.
A Hamiltonian path that is also a graph cycle is called a Hamiltonian circuit
(or Hamiltonian cycle)."
http://mathworld.wolfram.com/HamiltonianPath.html
"A Hamiltonian circuit,
also called a Hamiltonian cycle,
Hamilton circuit,
or Hamilton cycle,
is a graph cycle (i.e., closed loop)
through a graph that visits each node exactly once ...
By convention,
the trivial graph on a single node is considered to possess a Hamiltonian circuit,
but the connected graph on two nodes is not.
A graph possessing a Hamiltonian circuit is said to be a Hamiltonian graph.
The Hamiltonian circuit is named after Sir William Rowan Hamilton."
http://mathworld.wolfram.com/HamiltonianCircuit.html
"Hamilton paths are named after the renowned Irish mathematician (and astronomer)
Sir William Rowan Hamilton who lived from 1805 to 1865.
Hamilton was a child prodigy.
He could read English, Hebrew, Greek, and Latin by time he was four years old.
In addition, he wrote poetry and maintained close friendships with Wordsworth and Coleridge.
Hamilton became Professor of Astronomy at Trinity College in Dublin,
Ireland when he was twenty-three years old."
http://www.ctl.ua.edu/math103/hamilton/alittle.htm
http://www.maths.tcd.ie/~nhb/hamilton.php