Anamorphic widescreen hasn't been 2.35:1 since the 1970s. Modern widescreen, whether anamorphic or 35mm 3-perf, is 2.39:1, sometimes called 2.40.2.35 to 1 was established by an anamorphic system called CinemaScope. Anamorphics are ways of optically ‘squeezing’ one shaped image onto another, a process later reversed during projection.
Anamorphic was invented to create a wide "spectacle" image using a single camera and projector, instead of the multiple cameras and projectors used by systems like Cinerama. The wide image was used to create a spectacle that would draw audiences away from their TVs and back into the cinemas. (Like IMAX and 3D today.)
Many modern digital films shoot Super35, and crop a 2.39:1 widescreen frame out of the middle, but use the full-frame for non-widescreen home video.