The word flaw ("imperfection") has contradictory roots. It's the first part which was most confusing: it had a myriad of meanings proposed by all my sources, including a "spark", a "piece of snow", and a "splinter". This is extraordinarily confusing to me at least because I can't figure out how all these fit together. Supposedly, all are imperfect somehow: a single "flake" of snow is out of place by itself, a "spark" is an inconvenience and an annoyance, and a "splinter" is obviously bothersome and detracts from the perfect smooth surface of wood. How these transitioned to become each other is also very strange. Anyway, somehow "splinter" became "slab" as we go further back to the Old Norse word flaga. This traces back to the Proto-Germanic word flago, also meaning "slab", which goes to Proto-Indo-European as plak, meaning "flat", since a slab is flat.
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd