I did some reading and apparently Samuel A. Maverick voted for secession at the Texas Secession Convention and was a state legislator. For a time he was mayor of San Antonio. He negotiated the peaceful expulsion of US troops from Texas after Texas seceded. It seems he received cattle as payment for a debt and he didn't want them, didn't brand them, and eventually sold them. And, since he didn't brand the new calves and his hired hands didn't keep good watch of them, unbranded loose calves started being called Mavericks and the name came to mean someone 'outside the herd' or 'one who plays by their own rules' and eventually a classic TV series about brothers who sort of lived by their own rules. The hired hands were African-American and may have been slaves -- probably hired by him as opposed to owned by him.