There are a number of Chinese words containing the 白 character that all mean "nonsense" or "speaking nonsense":
白呼
夸白
白话
What's the significance of 白 in these words? 白 usually means "white", "clear" or "plain", so how did it become associated with nonsense? And is this related at all with the word 扯淡, which also means nonsense but originally meant 淡化 (water down)?
谈笑有鸿儒,往来无白丁
, 白丁 is a man who has no scholarly honor or official rank in the feudal age, i.e. commonly who is uneducated. 白丁 was so-called because they usually wear white coat. And in一穷二白
, similarly, 白 means the undeveloped status of culture. So, in 白呼, "uneducated talk" => "senseless chat".