Any idea where the phrase at sixes and sevens came from, and what it really means?
Phrase at sixes and sevens "hazarding all ones chances," is first in Chaucer, perhaps from dicing (the original form was on six and seven) and could be a corruption of on cinque and sice, using the French names (which were common in Middle English) for the highest numbers on the dice.
The Phrase Finder supplies that cite as follows:
The earliest citation in print is Chaucer's Troilus and Criseyde, 1374:
Lat nat this wrechched wo thyn herte gnawe, But manly set the world on sexe and seuene.
If things had stayed that way the origin of the phrase would be fairly cut and dried [...]. As we know though, it is now given as at sixes and sevens, having mutated via at six and seven, and the current meaning refers to a state of confusion, disorder or disagreement, not one of risk.
There's no question of these different versions arising independently, the movement from one to another was gradual and they overlap each other in time. The first appearance in print of at six and seven is in 1535 and the last citation of on six and seven in 1601. The first appearance of at sixes and sevens was in 1670, in Leti's Il cardinalismo di Santa Chiesa, translated [...] by G. H., 1670:
"They leave things at sixes and sevens."
Edit: in reply to your comments, the current meaning of the phrase is "in a state of disorder, confusion, dispute or disagreement" (see e.g. Merriam-Webster, Wiktionary, or the aforementioned Phrase Finder link).
Perhaps the phrase started before the great dispute between the two City Livery Companies the MERCHANT TAYLORS and the SKINNERS'COMPANy, but this history is probably the most reliable It was a royal requirement that the Mayor of the City should process from the City of London to the City of Westminster(seat of the monarchy) each year to present himself to the Monarch. The main highway beteen the two cities was the River Thames, and rivalry between companies was ferocious as to the order of precedence. A long=standing dispute between these two Companies as to who was sixth and who seventh in the processsion of barges, resulted one year in blows and bloodshed. They took their dispute to Mayor Billesden who decreed, with great wisdom, that the two companies should be sixth in alternate yearcs AND that each company should entertain the Master and Wardens of the other company to dinner yearly on the principle that those who dine together cannot remain in enmity. This was in 1484, and it worked! The dinners have continued unbroken since - THUS, the oldest dining club in the world (500th anniversary in 1984!) and The expression ALL AT SIXES AND SEVENS, The mayor still processes annually, but now it'a The Lord Mayor's Show.