I tend to take credit for introducing the term “baybilly” in the local New Jersey context in my mid 1990s writings. Of course, I have no way to know whether I was the first to use the term here. I had not heard the term used in New Jersey before those years. I vaguely recall reading about the term used in a southern state earlier. In fact, in 1889 the California State Agricultural Records show a race horse named “Bay Billy” The same record also shows a horse named “Nigger Baby” so this source might not be anything we wish to cite as a reference today. In the early 2000s (I think 2003) we had a fishing T-shirt printed for the business with the word “baybilly” and that seemed to boost the term’s local use.
Lately I notice that the term seems to be more popular, apparently fueled by pop culture and social media. The topic came up today because the term was used in a comedy video that used the term in association with Millville New Jersey and nearby southern communities.