"God of the gaps is a type of theological fallacy in which gaps in scientific knowledge are taken to be evidence or proof of God's existence. The term was invented by Christian theologians not to discredit theism but rather to discourage reliance on teleological arguments for God's existence.[1]

The term goes back to Henry Drummond, a 19th century evangelist lecturer, from his Lowell Lectures on the Ascent of Man. He chastises those Christians who point to the things that science can not yet explain—"gaps which they will fill up with God"—and urges them to embrace all nature as God's, as the work of "... an immanent God, which is the God of Evolution, is infinitely grander than the occasional wonder-worker, who is the God of an old theology."[2][3]"
http://en.wikipedia.org/wiki/God_of_the_gaps