jocular term for "clerk, writer," by 1820, from pen (n.1) + driver.
The Author goes on, and tells us, "that the two thousand hogs were not driven into the sea by evil spirits, but by the two madmen, who, in one of their frantic fits, frightened them into it."— But is it not more than intimated that the men were restored to their right mind before the hogs took to their heels? Besides, that two madmen should drive two thousand such ungovernable creatures as hogs one way, does, I think, exceed the belief of any hog-driver on the road, if not of the pen-driver in his closet. [introduction to "Beelzebub Driving and Drowning his Hogs," a sermon on Mark v.12, 13, by James Burgess, 1820]