It was suggested by an actual personality.

In an adjoining town to Cleveland there was a snake charmer who called himself Artemus Ward, an ignorant witling or half-wit, the laughing stock of the countryside.
Browne's first communication over the signature of Artemus Ward purported to emanate from this person, and it succeeded so well that he kept it up.

He widened the conception as he progressed.

It was not long before his sketches began to be copied and he became a newspaper favorite.

He remained in Cleveland from 1857 to 1860, when he was called to New York to take the editorship of a venture called Vanity Fair.