That the word priority wasn’t used in plural form (i.e. priorities) until the twentieth century?*
Priority means “precedence in order, rank or dignity,” according to the SOD of ’44. Imagine a state dinner, where all the guests are to be seated according to the precedence of rank or title. Now imagine that more than one guest has been given “top priority”. What happens? Musical chairs, and probably a diplomatic incident. (Two of the blokes above have come prepared with crossbows: one imagines they will have less trouble finding a seat than some.)
Now, while seating problems can frequently be solved with the introduction of a round table (nice one, King Arthur), life is more complicated. What have we invited into our lives – and are we sure we’ve got the seating plan worked out?
*source: Essentialism: The Disciplined Pursuit of Less, Greg McKeown, p.16