bladder

From Middle English bladdre, bleddre, bladder, bledder, from Old English blæddre, a variant of blǣdre, blēdre meaning 'blister, bladder,' from Proto-West Germanic *blādrā, from Proto-Germanic *blēdrǭ, *bladrǭ, meaning 'blister, bladder.'

The Old English form already carried both senses — 'blister' and 'bladder' — showing the word long described any thin-skinned, fluid-filled swelling rather than one specific body part.

The facts don't name a specific surviving cognate beyond the Germanic root forms themselves, so no further connection can be drawn here.