Great piece. Personally, I think the word came from the word custom as in to imply a person would return over and over again. I've worked in retail and this always seemed like a question asked to you when you applied for a job. I always seemed to muttered something like "no, not exactly but with some effort and input one can make the customer believe they are always right." I can't think of the chain retail store that trained their employees to use code words when taking about customers nearby. They apparently used the word "guests" when talking about paying customers and used the word "customer" when they suspected one was stealing or trying to abuse their company policy. My experience is that corporations or companies always want to profit over everything else and possibly the person or company that came up with this used this as a marketing tactic to gain trust and do sell whatever they were selling.