stavesacre

staves·a·cre   (stāvz'ā'kər)    n.   A larkspur, Delphinium staphisagria, of southern Europe, with greenish-white flowers. The poisonous seeds of this plant, formerly used medicinally as an emetic, a cathartic, and an external parasiticide. [By folk etymology from Middle English staphisagre, from Latin staphis agria, from Greek staphis agriā : staphis, stavesacre + agriā, feminine of agrios, wild; see agro- in Indo-European roots.]

stavesacre 

Main Entry: staves·acre
Pronunciation: 'stAv-"zA-k&r
Function: noun
1 : a Eurasian plant of the genus Delphinium (D.staphisagria) having racemose purple flowers
2 : the ripe seeds of the stavesacre that contain delphinine, are violently emetic and carthartic, and have been used to kill headlice called also staphisagria