Here's the breakdown:
* "Bang-off" or "Bangtail": In the 19th century, "bang-off" or "bangtail" was a term used for horses whose tails were cut straight across, often to make them appear fuller. This was a common practice, especially for show horses.
* The resemblance: The similarity between a horse's "bangtail" and a hairstyle cut straight across the forehead was readily apparent.
* Adoption by humans: People started using the term "bangs" to describe a similar style of fringe on human hair, again emphasizing the straight, blunt cut.
Therefore, the term likely originated from the visual association with horses' "bangtails" and the emphasis on the straight, abruptly cut nature of the hairstyle.
While there are other, less likely, theories (such as the sound of a barber's shears or a reference to bangs on clothing), the horse-related explanation is the most credible and widely accepted.