This is an irregular feature - both in frequency and oddness - dedicated to a word I came across that I have never previously used.
heortology (He-ore-TAH-loh-gee) n. The study of the origin, historical development, and significance of the seasons and festivals of the ecclesiastical year.
Derived from the Greek words heorte ("festival") and logos ("knowledge"), heortology specifically refers to the study of sacred festivals, especially understanding the history of their origin and how they have evolved over time. Christmas, for example, did not become a part of the Church's ecclesiastical festivals until the fourth century, and has its roots in earlier pagan winter festivals.
The word is typically used in a Christian context, but could also be used in an analysis of the festivals of other faiths.