[jes]

I had not heard the term either. Based on what others have written here, the position sounds similar to, but not exactly the same as, what manufacturing companies call an expeditor: A person assigned to the manufacturing floor who gets hot (late) orders finished and shipped as soon as possible.

[JJzD]

An expeditor works on (late) customer orders, and does what is necessary. The water spider supports the people working on customer orders.

I'd consider that a major difference, but your mileage may vary :)

[tyingq]

It was "rover" or "free safety" a long time ago when I worked in a factory. Both borrowed American football terms that seem to fit reasonably well.