This attractive little flower is the Mountain or Hedgerow Cranesbill (Geranium pyrenaicum).
It's growing in my garden as a low-lying hardy perennial. I didn't plant it, it must have found its own way there. Although it grows as a wildflower in the UK and may be a native plant — the jury's still out on this, though — it is widely cultivated as a garden flower and this one is presumably an escape from a neighbour's garden.
Its scientific name Geranium is because its seed-pods look like tiny cranes bills. (yeranos [γερανός] is Greek for crane, in both senses of the word).
So what about the flowers we usually call geraniums? Well, they should arguably be called storksbills, because their scientific name is Pelargonium, from Greek pelargós (πελαργός), 'stork'.
But calling pelargoniums geraniums is here to stay, I can't see it changing now. In all began in 1753 when Carl Linnaeus placed some exotic plants, new at the time to European science, in the same genus Geranium as the native cranesbills. 40-odd years on Charles L'Héritier realised this was a mistake and created the genus Pelargonium for the new plants. But by then the damage was done and the confusion seems to be embedded in the majority on languages.