The company's output of iron ore, as well as copper, zinc and nickel, surged in the last three months of 2009 because of strong demand from Chinese carmakers and construction companies.

VOA: standard.2010.01.21

Why? Well, out presumably 'cause it's output, a because it's the first letter of the alphabet.

为什么？也许是因为out代表是输出吧，而a则是字母表的第一个吧。

哈佛公开课 - 计算机科学课程节选