So, I did research it myself, and though you can't trust everything you read on the internet, Wiki is a quick way ...so,here it is:

King Sr. became leader of the Ebenezer Baptist Church in March 1931. With the country in the midst of the Great Depression, church finances were struggling, but King organized membership and fundraising drives that restored these to health. By 1934, King had become a widely respected leader of the local church. That year, he also changed his name (and that of his young son) from Michael King to Martin Luther King (though he never changed his name legally) after becoming inspired during a trip to Germany by the life of Martin Luther (1483–1546).