Brendan, looks like it’s predominantly a sailing/nautical term - if you need to know more than is in wordreference bilingual or Collins, you might have to check specialist dictionaries, or ask a sailor.

 https://www.wordreference.com/fren/lofer 

https://www.wordreference.com/enfr/luff

 https://www.collinsdictionary.com/dictionary/english/luff