Tim Bowen sheds some light on the origins and definition of the phrase at sixes and sevens.
If you are at sixes and sevens you are in a state of total confusion, disorder or disarray. You might say “When it happened, I didn’t know what to say. I was at sixes and sevens for a moment”. It is often used as a metaphor in a sporting context as in “The United defence was at sixes and sevens and it wasn’t long before City scored a third goal”.
There are various theories about the origin of this expression, none of which can be verified, as is often the case with word origins. Some people believe that the expression has its origin in the fact that, added together, the two numbers give the unlucky number thirteen. Others say that it comes from the fact that two members of a medieval trade guild in London quarrelled over which one had precedence and should be sixth in order of importance in the guild, the president of the guild settled the matter by ordering that each one should be sixth one year and seventh the next, thereby resolving the problem but also creating a considerable amount of confusion.