It's possible he misspelled or misremember the name, and that Norelco is not the right name.
As for epigenetic, could be a lot of things. Exposure to freezing temperatures while a seed. Exposure to freezing temperatures while a seedling. Constant exposure to freezing temperatures. All of these, but with cold instead of freeze?
There will probably be some physiological barriers that are harder to overcome than others. In most trees and shrubs, flowers and floral buds are the least hardy part of the plant. Getting a plant to resist freezing might still not mean that its flowers/fruits will survive under 40F. "Cold resistance" molecules might not distribute evenly within the plant.
How does the supposed frost/cold tolerance work, anyways? Some species will fight cold by generating heat (i.e. skunk cabbage). Some species will fight nucleation of ice crystals by modifying their internal solutions so as to lower the freezing point (ex. increased sugar content in quinoa, supercooling). I suspect some resist by modying their susceptibility to cell burstage due to freezing. Glycerol can be added to a yeast solution to prevent crystal formation (is this another example of supercooling?). I can't give examples, but it's possible that some species may be able to insulate themselves, to offer minor protection from cold/frost (though given how thin plants are, this effect is probably going to be extremely minor at best).
It's known that brassicas respond to frost by sending sugars into their leaves. I'm no expert on the subject, but I'm getting the impression that storing sugar into leaves is the main form of frost tolerance in plant species. By extension, testing tomatoes for higher sugar content in their leaves would possibly work as a proxy for frost resistance, and measuring sugar content following various treatments (seed exposure to frost/cold, seedling exposure to frost/cold, plant exposure to frost/cold, non-exposure to frost/cold) would probably be able to give hints on the underlying mechanisms.