well...sometimes it might seems a bit odd...but if u know more about it(not just the grammar,meaning)...like the story behind it/western culture etc..those words are interesting in a sense.
(ps westerners get a different sense of humor...so u can't stick with the literal meaning)
For example...like the word'one-night stand'....if i remember correctly..it's orginated from the band culture...when there's a guest band come (usually those on tour)...they will perform in the house(standing on the stage) for 1 night...and then move on...and it's called 'one-night-stand' .
Therefore ppl apply this term to a single causual sex...meet once and move on... u get the meaning?