[badsectoracula]

Nitpick but the genre existed before - Amnesia is a first person horror adventure game and the Penumbra series was their first attempt with almost identical mechanics. However even before there was Call of Cthulhu - and Thomas Grip's (Frictional's programmer) own Unbirth game[0] which was cancelled but they demo uploaded (the downloads do not work but you can find it at the archive[1]). Unbirth feels like a very unfinished Penumbra without the physics stuff (but the horror adventure game elements are still there).

And of course there were similar games going back in time, e.g. Realms of the Haunting [2] and i'm sure you can find many others.

[0] https://unbirth.frictionalgames.com/

[1] https://archive.org/details/unbirth_alpha

[2] https://www.youtube.com/watch?v=wzT27LXpoyc