The most obvious names to honor this day of course come directly from the name - naming a boy Martin, or Luther, or even King.
Luther is the most obvious honor choice, it will probably lead to the question "like Martin Luther?" Yes. Exactly. Luther means "Soldier of the people", very fitting.
Martin is the more subtle option, there are many Martin's in this world and someone would have to tell their naming story for the connection to be made. Martin is Latin and means "servant of Mars" - the war god.
King as a first name is of course the most aggressive and edgy, it would not fly everywhere as some countries do not allow titles as first names, but here in the U.S. it would strike us as odd, but not over the top, especially if the reference was brought up.
The two other names directly related to Martin Luther King that I discovered would be Dexter, after the Dexter Avenue Baptist Church where MLKjr lead, or the word as a name option Dream after the famous "I have a Dream" speach.
A speech, which by the way, got most of its bulk when fellow activist Mahalia Jackson shouted out "tell them about the dream," (at least in legend if not fact), causing MLK depart from his script. Mahalia is Hebrew and means "tender one".
After MLK was assassinated, his wife Coretta Scott King carried on the work. Coretta is a version of Cora, which means maiden. Scott means "from Scotland" or "Scotsman".
While MLK was the most famous civil rights activist here in America, there are plenty of other options to choose from. Some options:
Howard Thurman - MLKs mentor and fellow activist, speaker of the inspiring/famous but often mis-credited quote ""Don't ask yourself what the world needs. Ask yourself what makes you come alive and then go do that. Because what the world needs is pe"ople who have come alive."
Bayard Rustin - A follower of Gandhi who taught MLK about nonviolence, helped to organize the March on Washington.
Ralph Abernathy - Founder of the Southern Christian Leadership Conference, which MLK lead and was used to organize most of the big nonviolent protests.
Roy Wilkins , Whitney Young, Philip Randolph, John Lewis, and James Farmer Jr - The other main organizers of the March on Washington, and representatives of the "Big Six" civil rights organizations of the day.
Of course we can't leave out the other women!
Famously, Rosa Parks would not give up her spot on the bus, but it was actually Claudette Colvin, a fifteen year old, who first refused to obey the bus segregation. And it was Aurelia Browder whose case of sitting on the wrong part of a bus was taken to the supreme court to help overturn the Jim Crow laws.
Enough history, back to these names. I would am particularly interested in Claudette, which is a feminine version of "Claude" and it manes lame. Aurelia, what a beauty, is Latin and means "Golden." Bayard is French and means "Auburn Hair". I think Rustin could also make a lovely first name for a boy. It means "Rust's Estate" and is a last-name-as-first-name.
Of course, while the civil rights movement is history, there is still many groups fighting for equal rights, most notably, those with different sexual preferences. If you are looking for a more modern inspiration for a civil rights activist, try something from the following list:
Harvey Bernard Milk
I can picture a little Harvey or Bernard running around, can you?