According to Google Scholar, the phrase "artificial intelligence" was first used in a 1759 paper on "Large scale parallel data mining".

http://scholar.google.com/scholar?q=+%22artificial+intelligence%22&as_ylo=1750&as_yhi=1800

In fact, it was first used in 1955 in a Dartmouth proposal.

http://scholar.google.com/scholar?q=Proposal+Dartmouth+Artificial+Intelligence+&as_ylo=1955&as_yhi=1955