a group of soldiers assigned to an extremely dangerous duty
Word origin
C16 (in the obsolete sense): changed (by folk etymology) from Dutch verloren hoop lost troop, from verloren, past participle of verliezen to lose + hoop troop (literally: heap)
forlorn hope in American English
1.
a group of soldiers detached from the main group for a very dangerous mission
2.
a desperate undertaking; enterprise with very little chance of success
3.
a faint hope
Word origin
altered < Du verloren hoop, lit., lost group < verloren, pp. of verliezen, to lose (akin to forlorn) + hoop, a band, group; akin to heap; (sense 3) through confusion with hope