Blackmoor evolved from Arneson's wargaming sessions, after he began to expand them to include ideas from The Lord of the Rings and Dark Shadows.
It was created in 1882 for the lawyer and Liberal politician Roundell Palmer, 1st Baron Selborne, along with the subsidiary title of Viscount Wolmer, of Blackmoor in the County of Southampton.
The first published version of the sahuagin appeared in the 1975 Dungeons & Dragons supplement, Blackmoor by Dave Arneson.