the.com/flanger

means A device or effect that creates a swooshing, whooshing sound by mixing an audio signal with a slightly delayed copy of itself, the delay constantly shifting.

from Rooted in 'flange,' the rim or projecting edge on a wheel or pipe — the mechanical sense of a protruding lip. The audio meaning reportedly comes from a studio trick: engineers would press a finger on the rim (the flange) of a tape reel to slow it slightly against an identical playing copy, creating that shifting, metallic delay. The story is often credited to figures like Les Paul, though exact origins of the technique and the term's first use are murky. By the time the effect went electronic in the 1960s-70s, 'flanging' had stuck as its name.