Proto-Indo-European *pleu- "to flow" became Proto-Germanic fluǥ-, "to fly" (becoming English fly). What the OED says is a dissimilated form, fluǥ-laz, became Old English fuȝol then English fowl (compare German Vogel "bird").
A suffixed form became Greek πλοῦτος ploutos "wealth, riches" (from the sense of "overflowing"). This was Latinized as Plūtō, god of the underworld, "from the belief that the underworld was the source of wealth from the ground".
More about fl- words later, probably.