"Yisse" - (slang) "Cool!", "Awesome!". An elvish word “yissen’” means “sweet”. Sounds a bit like the English “yes”. After a while it became a popular slang phrase in New-Yorkshire.
"...means “warm”..." – an incorrect translation. Elvish is not her native language.
"Bghuuk-duk" - (dark) “bullshit”.

"Darks" – even though here it’s used to describe the members of a certain dark organization, this derogative term is usually used to describe any member of the dark people.

"suits", sometimes "habit" or "zoot" - (eng. slang) in this case, concealed armor.