The earliest reference to Beersel is probably in a charter of King Charles the Bald, which was enacted on 23 March 847 and donated "BERSALIS in pago bracbantensi" to the Saint-Amand Abbey on the river Scarpe. The toponym means 'dwelling on poor or swampy soil'.
Unlike in the case of many other locations, watercourses did not play a determining role in the development of Beersel. The main determining factors in the establishment of Beersel were the hillside, on which the village is located, the presence of many water sources, fertile fields and meadows, and also the road system.
The street that connects the village of Beersel northwards with Calevoet and the Heerweg, and southwards with the Senne Bridge in Lot, is an old road, as is the Heerbaan that lies to the east of it and once connected various regions. The passage of the Senne river through Lot has historically been of key importance. Excavations in that area revealing remains dating back to the Gallo-Roman period confirm this.
The Senne bridge in Lot is undeniably a crossing of old roads. The two roads along both sides of the Senne connecting Halle with Brussels, and the street leading from Uccle over Beersel village to Sint-Pieters-Leeuw and the rest of the inland, all come together at that point, along with a few other locally important roads. The scars along this route referring to Beersel's oldest urban settlements are numerous. We find them near roads connecting with the Heerweg and in places near water springs, fields and meadows.
We find them in the vicinity of:
- the Dachelenberg, close to the Dachelborre and the primitive Kelle (spring). And near a 'MOTTE' (a natural or man-made earthen mount surrounded by water) named 'd'Auburg';
- the Heiberg, where the current village centre is located - with three village springs called the Roodenpoel, the Puttebron and the Papaardbron, and the roads to Alsemberg and Linkebeek which both connect with the Heerweg;
- the CASTLE, where we can find the brook the Sint-Lambrechtsbeek and the street to the heathland the Laar(heide), where another settlement area with an old motte is located along the Heerweg.
In all these places, all elements required to establish a village are present. In the case of Beersel, ancestors chose to settle on the Heiberg, a very favourably situated observation point along an undulating hillside, from where one could overlook the wide surroundings from Halle to Brussels. Surroundings which the Heiberg, located between two castle centres, completely dominates.