Various forms of the word roup have long been circulating in Scandinavian countries, but it has had limited penetration into the English speaking world. It does appear rather frequently in Scots, where the word roup had multiple meanings, not all of them, apparently, related to the Scandinavian.
1. Roup can refer to an auction, or the act of selling something at auction. This was particularly used as an element in compound words, including: cross-roupin' (sale by auction at the public cross); roup-day (the day of an auction); rouper (one who sells goods at an auction); roup-folk (anyone attending an auction); roup-green (the field in which an auction is held); rouping-wife (a woman who buys goods at auction to resell); roup-wife (a female auctioneer); and roup-roll (the list of goods to be auctioned). This sense is the most common, and probably does descend form the Scandinavian root (see 2.).
2. To shout, roar, or croak; to proclaim in a loud voice. This sense is of direct Scandinavian origin, and it probably also the origin of the sense of to sell by auction.
3. A number of diseases affecting poultry, including: vitamin A deficiency; inflammation and mucous discharge caused by parasites in the windpipe; or swellings on the birds' rump glands. It appears that the most common/modern use is to refer to respiratory infections, although this should not be assumed -- making this usage fairly useless without context. This origin of this sense is of unknown, although it is probably related to 2. or 4.
4. Hoarseness, huskiness of voice. This is believed to be of imitative origin, and not related to the words above. The adjectival form is roupit ('he is roupit').
5. Sea weed, perhaps particularly kelp. It was used as a synonym for ore-weed. Roupie was also in use to mean overgrown with seaweed. This origin of this sense is of unknown.
6. To plunder; to devour; to explore.
7. To vomit.
8. a heavy mist. Roupy-weather was also used to mean 'a fog so thick that it makes one hoarse'.
Before the days of standardized spellings, the forms roop, roupe, raup (Northern England), rolp, rowp,raup, and rawp were also used.