bell-bottoms (n.)youdaoicibaDictYouDict
type of trousers, 1882, from bell (n.) + bottom (n.). Distinguished in the late 1960s from flares by the shape of the expanded part (flares straight, bell-bottoms curved).
flare (n.)youdaoicibaDictYouDict
"a giving off of a bright, unsteady light," 1814, from flare (v.). This led to the sense of "signal fire" (1883). The astronomy sense is from 1937. Meaning "a gradual widening or spreading" is from 1910; hence flares "flared trousers" (1964).