question about purple dead nettle - lamium purpureum

[Salty Thumb of Death]

Hello,

Does anyone know where I can find some information on purple dead nettle?  
Plants.usda.gov just gives some taxonomy.

Does anyone one know why it's called dead nettle?  Something to do with 
death or is it a corruption of some other language?  Is it true that it's 
presence indicates heavy metals (particularly lead) in the soil?  From 
hearsay, I've gathered that it tends to grow in 'wasteland' which makes 
sense if the part about heavy metals is true.

Hopefully this is a good group to pose this question.