Joshua

3 minutes ago, 宇崎ちゃん said:

I used to live in the Netherlands for the first 26 years of my life, I really never heard of it before.
Maybe it's no longer used (colonial Dutch?) or just very recently added?

"Laster" is used in Netherlands Dutch too in more legal situations.
And the sentence we're translating is a legal term.

I was not aware of the legal context, I also saw someone mentioning a birthday present. Achterklap is a normal Dutch word but maybe a little bit outdated. It's closer to "gossip" but I thought it worth mentioning since they're normally used together, at least they were when I lived there which was eight years ago for 32 years...

2 minutes ago, 宇崎ちゃん said:

I don't think I've ever heard of that word before.

a previous South African translation uses "laster" which is a perfectly fine Dutch translation. However in The Netherlands "achterklap" is much more often used in this specific combination...

Dutch: leugen en achterklap