"To those who know the history of the word, applying it to Mr. McCain is a bit of a stretch — and to one Texas family in particular it is even a bit offensive.

“I’m just enraged that McCain calls himself a maverick,” said Terrellita Maverick, 82, a San Antonio native who proudly carries the name of a family that has been known for its progressive politics since the 1600s, when an early ancestor in Boston got into trouble with the law over his agitation for the rights of indentured servants.

In the 1800s, Samuel Augustus Maverick went to Texas and became known for not branding his cattle. He was more interested in keeping track of the land he owned than the livestock on it, Ms. Maverick said; unbranded cattle, then, were called “Maverick’s.” The name came to mean anyone who didn’t bear another’s brand."

Who You Callin’ a Maverick?
By JOHN SCHWARTZ, NYT, LINK
Published: October 4, 2008

That said, what does it mean to be a McCain?