Both words emerged centuries ago in Old English. Neither pushed out the other and now they are used interchangeably, although proportion of usage does vary between different English speaking nations.
Fall/autumn is unique among the seasons in that it has two names where the others all have a single name. What makes this season so special?
It turns out that there really doesn’t appear to be a good reason for the extra name, other than the fact that two English names for the season emerged and a universal preference was never established. There seemed to be more agreement with the names of the other seasons.
Before there was fall and autumn, the 3rd season of the year was generally called harvest. When the English population began to migrate from the farms to cities in the 17th century, the harvest became less important to their daily lives.
During the 1600s, more people began leaving rural farmlands to move into larger, metropolitan cities. Without farming, the term “harvest” became less immediately applicable to the lives of city-dwellers, and subsequently, “fall” and “autumn” emerged as two new names for the season.
Where Does Autumn Come From?
According to Merriam-Webster, autumn first came into Old English in the 14th century from the Latin word autumnus. The root of this word may be a reference to “the passing of the year”. According to Wordsense.eu it is “From earlier auctumnus, from Proto-Indo-European *h₃euǵ- (“cold”)”.
What About Fall?
The name fall traces its origin back to 16th century England. It seems to be a contraction of the phrase “fall of the leaf”. Fall and “fall of the leaf” were seen by some to be a more poetic descriptor for the season and gained in usage. However, it took some time to catch on and didn’t make it into a dictionary until 1755.
America vs. Britain
Both terms originated in England, but like many other parts of the English language you will find divergence in usage. You will now find that fall tends to be the preferred term for most people in the US and autumn is preferred in the UK.