Why does 拉倒 mean "forget about it"?
拉倒


In a mandarian Chinese, this really means "pull down". However the words are constructing a certain dialect's pronunciations, so you cannot split words from words to understand its meaning. In ShangHai dialect, this means "give up because of no choices or no other ways", "Have to do something narrowly"：

【e.g】既然你不肯给我东西，那就*拉倒*了。（=那就算了）
Since you won't lend me what I want, that's all for that.