There was indeed a Flying Orchid program for travel arrangers, but it had nothing to do with the designator "FO". FO does indeed stand for "Flys Often" and was the designator for the original Medallion member (back before there were multiple Medallion levels). To this date, it remains the designator for Silver Medallion. The original qualification requirements for Medallion level were much the same as they are today for Silver Medallion.

Funny how an airline really used to value people who flew 25,000 miles a year on the carrier (and at that time there were no MQMs and each flight earned a minimum of 1000 miles), which was the qualification requirement for Medallion level. Now, fly 25,000 miles and you mean very little to the carrier.