Short answers, pulled from the story.
George Holyoake coined the term secularism in 1851 while standing before a crowd in Britain. Holyoake was not an atheist but sought a term that allowed believers and non-believers to cooperate in building a society where the state did not dictate spiritual truth.
France enshrined laïcité into law in 1905 to establish a system where the state does not recognize, fund, or endorse any religion. This legal supremacy of the state over religion restricts the use of religious iconography in public spaces and schools without exception.
Mustafa Kemal Atatürk adopted secularism as a state ideology in Turkey in 1923 to modernize the country by stripping the state of its Islamic character. This Turkish model of secularism, or laiklik, was initially modeled after French laïcité but evolved into a unique system.
Roger Williams founded the Providence Plantations in 1636 as a settlement with total freedom of religion. This radical experiment in a time when dissent was often punishable by death laid the groundwork for a world where the state could exist without a state religion.
Secularism is a philosophy that seeks to interpret life based on principles derived solely from the material world and focuses only on temporal and material concerns. It is a rejection of the supernatural and a belief that the universe is made of matter and energy without the need for a divine being.