In Ruby, why is the accumulator called memo in the inject/reduce methods?

Question

Out of curiosity, why is the accumulator called memo in the inject/reduce methods? Is there some context/history behind its naming? Does it actually mean "memo" or does memo stand for something?

http://ruby-doc.org/core-2.0/Enumerable.html#method-i-inject

http://ruby-doc.org/core-2.0/Enumerable.html#method-i-reduce

Answer 1

"memo" means in memory,that inject uses throughout its full iteration to hold the intermediate object state,to use it for its next iteration.