I don't believe Thanksgiving is a "holiday of religious origin." It does
not mark or celebrate a religious event. Nothing of note in any religion
occurred on that date. Thanksgiving was a date set aside by a group of "new
Americans" to jointly and in unison cease all normal activity and, with
grateful hearts, to recognize and say "thank you" to G-d for their survival
through rough times in a new land. This makes it a holiday of [national
and] religious significance - but not of religious origin.