DeWayne was actually the first respelling of Duane to be regularly used as a male given name in the United States. The main impetus for Duane's use as a first name was James Duane (1733-1797) who was a mayor of New York City, member of the New York state legislator, and federal judge at different points in his life. The form DeWayne probably developed when people confused Duane with Dutch surnames like DeVries and DeWitt, the latter being well-known as a given name in New York through DeWitt Clinton (1769-1828) who was himself mayor of New York City three times and governor of New York twice. There are 11 men or boys named DeWayne in the 1850 U.S. census, the oldest born in 1822.
The spelling is utter crap, and the name itself always sounded annoying to me. I can already imagine someone pronouncing this in an annoying, loud-mouthed, nasal voice with an irritating grimace.