Some legal scholars, such as John Baker of LSU, theorize that Madison's initial proposed language—that Congress should make no law regarding the establishment of a "national religion"—was rejected by the House, in favor of the more general "religion" in an effort to appease the Anti-Federalists. To both the Anti-Federalists and the Federalists, the very word "national" was a cause for alarm because of the experience under the British crown. During the debate over the establishment clause, Rep. Elbridge Gerry of Massachusetts took issue with Madison's language regarding whether the government was a national or federal government (in which the states retained their individual sovereignty), which Baker suggests compelled Madison to withdraw his language from the debate.
Why was a more general "religion" used in the language of the First Amendment? (If the question is unanswerable, say "unanswerable")
to appease the Anti-Federalists