This is the 2232nd most frequent Dutch word.
omheen
Around or surrounding.
Here, 'omheen' emphasizes going around something in a circular motion, with 'om' indicating the around and 'heen' adding the sense of movement.
Ik loop om het huis heen.
I walk around the house.
In this sentence, 'omheen' describes the placement of lights surrounding the tree, combining placement ('om') and enclosure ('heen').
Zij hangen lichten om de boom heen.
They hang lights around the tree.
'Omheen' in this context expresses something closely encircling an object, 'om' for surrounding it and 'heen' to enhance the visual image.