Is it Fall or is it Autumn?

The word autumn comes from the Old French word autompne (automne in modern French), and was later normalised to the original Latin word autumnus.There are rare examples of its use as early as the 12th century, but it became common by the 16th century.

Before the 16th century, harvest was the term usually used to refer to the season, as it is common in other West Germanic languages to this day. However, as more people gradually moved from working the land to living in towns (especially those who could read and write, the only people whose use of language we now know), the word harvest lost its reference to the time of year and came to refer only to the actual activity of reaping, and autumn, as well as fall, began to replace it as a reference to the season.

The alternative word fall for the season traces its origins to old Germanic languages. The exact derivation is unclear, the Old English fiæll or feallan and the Old Norse fall all being possible candidates. However, these words all have the meaning "to fall from a height" and are clearly derived either from a common root or from each other. The term came to denote the season in 16th century England, a contraction of Middle English expressions like "fall of the leaf" and "fall of the year".

During the 17th century, English emigration to the British colonies in North America was at its peak, and the new settlers took the English language with them. While the term fall gradually became obsolete in Britain, it became the more common term in North America.

So, either one you choose to use, use it while holding a cup of tea and wearing your favorite sweater!