Story Five: In ancient times, one thousand coins made up one "diao", and five hundred coins were called "half-diao" or "half-assed". Those worse than "half-assed" were called "two half-diaos", which is "er-bai-wu" or "two fifty".
Story Six:
In the past, silver was measured in units of ten taels to a lump, and five hundred taels to a packet. Two hundred and fifty taels would then be "half a packet", which sounds like "half crazy". Over time, people began using "er-bai-wu" (half crazy) to describe those who are always making a fool of themselves, speak improperly, are irresponsible, and handle things carelessly.