This is creeping thyme (Thymus serpyllium). In Irish it’s called ‘lus na mbrat’, which means the herb of the cloak.

The story is that, ages and ages ago, when the world was a different sort of place, there was a battle. And in this battle the great warrior Nuada, wielder of the sword of light, had his hand severed from him. So one of his physicians, Dian Cecht, made him a silver hand that could move and work just like his own hand. But the healer Miach, son of Dian Cecht, made a poultice for him that caused his hand to regrow.
This caused contention between the two physicians, the first claiming it was interference and the second claiming it was a better remedy. In a rage, the father murdered his son.
After he had been buried, his sister Airmid gathered 365 different herbs and laid them all on his grave. And over all of them she laid her woolen cloak. And from the grave, and from the cloak, and from the 365 different herbs, there grew this one new herb, spreading over everything in the shape of a cloak. 

In terms of pharmacology, the plant is very similar to the more common thyme, containing thymol, carvacrol, and other aromatic compounds. It’s a powerful antiseptic and decongestant.