I started out researching the why’s behind odd numbered hooks (9, 11, 13) and the seemingly more prevalent sizes (6, 8, 10). Came across a convoluted history of various hook manufacturers that lead to an effort of standardization….kind of.

The Fly Tying Forum offered up, in a discussion, a reference book (The Essential Fly Tier by Edson Leonard, Pages 1-24) that offers good basic information re hooks. Interesting add’l here @ Singlebarb

Fly Fishing Forum (h/t: shuck raider)