Bridget Wenlock was a famous arithmancer, noted for her groundbreaking theories on the magical properties of the number seven (FW).
Wenlock was very protective of her work and used a variety of methods to prevent anyone from seeing her writing, including invisible ink. Unfortunately, Wenlock was also very forgetful and often her methods prevented her from being able to understand or even find what she’d written down. Wenlock lived in the town of Tinworth in the 1200s (BoS).
Other canon notes and references
Wenlock's absent-mindedness prompted Miranda Goshawk to include anecdotes about Wenlock in her famous Book of Spells.
Students who are entering Hufflepuff house at Hogwarts are informed about famous members of that house, including Wenlock, who would have entered Hogwarts in 1213 (or possibly 1214).
Wenlock was known for her work on the number seven. Notice that both her first and last name are each seven letters long. -BB