A small blister on the skin, or a bubble in glass or water.
From Middle English blabbe, possibly from Old Norse blaðra or related to Old English blǽder (bladder). The word may derive from the visual similarity between a blister and a bubble—both are fluid-filled swellings.
In medicine, blebs are actually a serious problem in eye surgery—they're tiny fluid-filled bumps that can develop months after surgery and cause vision loss. The same word describes both a tiny skin irritation and a potentially sight-threatening complication!
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