It could've very well come from honey or possibly brown sugar, corn syrup, or even molassas. You can season the salmon with whatever seasonings you like, then smoke it, and then glaze it before serving. You can make a glaze by reducing fruit juices such as pineapple, orange, or cherry juice. Float a smashed garlic clove and maybe a piece of ginger as it reduces. Then add some salt and pepper, and a touch of honey. You can experiment with different juices, sweeteners, spices, even soy, teriyaki, hot sauces, or vinegars for different combinations.