Also known as Purple Dead-Nettle, because the hairy roundish leaves reminded someone of nettles that don’t sting. This tiny flower is one of the first to appear in the spring, or even in the middle of winter if it gets a warm spell. It continues to bloom for most of the season, and it adds the very decorative touch of deep purple leaves to set off the lighter pinkish-purple flowers.
For a more thorough description, see the Lamium purpureum reference page.