The bell bottoms referenced are alterations called “flares” where colorful fabric panels were sewn into the garment rather than manufactured whole cloth. To be clear, people knew bell bottom pants existed, but “flares” were what people wore. I believe everyone just started calling them bell bottoms because it was a generic term.
There’s a lot more to the recent past than you realize and not all of it is online.
>There’s a lot more to the recent past than you realize
listen youngster, bell bottoms were mid to late sixties worn by dirty hippies
while "flared slacks" are really a 70's item, often in polyester, worn by more mainstream types who wanted slacks (not pants), worn to the disco scene, etc.
The main difference would be bell bottoms belled in every direction, while flares were more front to back.
it is true in the early period of bell bottoms that many people would convert their straight leg jeans to bell bottoms by inserting a triangle in the inseam below the knee, often of a contrasting material, paisly/psychedelic/leather that type thing. As that was a bit unbalanced, a more ambitious style would do a bit of a spiral around the ankle and calf.
There’s a lot more to the recent past than you realize and not all of it is online.