I have always found it amazing that you can pull strapping so hard through the cord buckle and the cord strap does not back out. The two main secrets are in the coating and geometry. If your cord buckle is galvanized coated, a woven strap will back right out. Galvanized buckles lower the friction and are used for composite cord strapping like CC65 or CC105. Phosphorus coating acts like a sand paper, increasing friction. It is almost always used on woven cord strap, or on composite that ships on containers.
The other way to get more friction is with a ladder style lashing buckle. This rigid buckle does not bend, with the buckle legs clamping down to secure the strap. Instead it takes a long weave with the strap to put more surface area of the strap onto the buckle.