Martin of Tours. A lot of histories of him leave the hair part out, along with the part about how he didn't want to be a bishop, so he hid, but was betrayed by the honking of a goose. Ever since, on Saint Martin's day, they eat goose- I'm not sure which of them it's a jab at. Maybe both.
It was also a nod to Martin Luther King, whom I admire, and to Martin Luther, whose steadfast courage and determination to see things he knew was wrong set right deeply resonated with me. And a way of thumbing my nose at the Church a little, since, you know, Martin Luther and all. And several other things, too; taking on a new name is not a decision to be made lightly.