Willoughby

This name can also be a Feminine name, making this name Unisex. It's Feminine usage might be related to Willow.
According to the USA Social Security Administration, 10 girls and 0 boys were recorded with the name Willoughby in 2020.
https://www.names.org/n/willoughby/about
https://www.nancy.cc/baby-name/willoughby/
https://www.behindthename.com/name/willow [noted -ed]

I've only heard it used as a surname.

Despite it generally being seen as a male name, Willoughby is the name of my great great great great grandmother (born 1815 in Norfolk, England) and is primarily used as a female name in Norfolk from at least the early 1700s.