Simon, you have read this on the Fallkniven-forum on knifeforums.com. The term was probably coined by a German man called Görtz. He is a bit of a Fallkniven-nut and hunter. The 'Nordic Trinity' consists of a Fallkniven U2 folder, a Fallkniven H1 (actually, Görtz ownes three H1's) and a GB axe. This set up makes a lot of sense, with these 3 high quality tools you can do almost everything.
I was inspired by his Nordic Trinity and have the same set up, except for a Fallkniven F1 instead of the H1. The U2 folder is a delight. It only weighs 42 grams, you won't even feel you are carrying it around. The secret is in the steel used for the blade: powdered steel. It excells as a (fruit) paring and general food knife. You can throw sparks with a firesteel and it's a nice back-up.
For the middle part of the trinity the F1, H1 or even the S1 will do pretty good (I see you have a NorthernLights series). I love Fallkniven myself because they are such simple basic tools. The H1 and S1 are strong enough to split wood, but for real chopping power a GB-axe is the way to go, just get the size you think that will not add too much weight to the pack (GB Wildlife Hatchet should be fine). Nordic Trinity: investment will be around 160 GBP, depending on the exact set-up. You won't need anything else for tools.
You can read more on this thread:
http://www.knifeforums.com/forums/showtopic.php?tid/785459/tp/2/
And the plot thickens... the concept goes back a long time:
http://outdoors-magazine.com/s_article.php?id_article=179
