In traditional herbalism, Herb Robert is a remedy for toothache and nosebleed and in healing of wounds. The name refers to abbot and herbalist Robert of Molesme. Freshly picked leaves have an odor resembling burning tires when crushed, and if rubbed on the body the smell repels mosquitoes (and probably anything else including friends).
The active ingredient is tannin, a bitter compound called geranlin, and essential oils.
It was carried to attract good luck, and due to its analogical association with storks, to enhance fertility.