I think my little Vocabulary side project is starting to pay off. I was walking round the house last night (27 miles, every night) and I suddenly realised that "forlorn" sounds like the German "verloren".
Forlorn hope is a military term that comes from the Dutch verloren hoop, which should be translated as "lost troop": the Dutch word "hoop" is not cognate with English hope
(http://en.wikipedia.org/wiki/Forlorn_hope)
I would have thought there was a strong link between the Dutch and German, especially since "verloren" means "lost". However, it seems that the direct translation of "forlorn" into current German is "verlassen".
Hmm.