The lineage of Van Wersch (Vanweersch, Van Weerst, Van Weers etc) comes from the Belgium village Weerst. This word Weerst derives from the old Dutch word war-waer-weer-wer.
And this means to defend. The ending st comes from stede in Dutch or town in English.  So you have then: Weerstede, Weerstee, Werste, Werst, Weerst
with other words: a place / town to defend.
The French name Warsage for this village was mentioned in 1150  when the prince bisshop of Liège bought the munitionem de Warsage. This purchase was confirmed by pope Adrian in 1155 in castris, villis, burgis ... Warsage and by emporer Frederik I Barbarossa, in a charter from the same year with the words  castris Warsage by which a fort was mentioned.
(Ceijssens 1,47 e.v.)

Jos Crott has a different explanation of this surname Van Wersch. In his book Familienamen in Limburg (Familynames in Limburg) from 1995, he writes:

The name Van Wersch derives, according to popular believe from Weerst, the local name for Warsage in the province of Liège. Nevertheless we think it is also possible that the name derives from the hamlet Wersch, at former times a spot beneath Weiden near Aachen. We must think that former hamlets consisted only of a few houses long time vanished. It is striking that this familyname appears above all things in Kerkrade, Simpelveld, Bocholtz and Vaals; towns that are so to speak lay close to Aachen. Furthermore there is a village Wersch near Cologne. We suppose that there could be two not related clans who have their own history. If this theory is right only familyreseach can prove.

Apparenly he did not known the book  800 Jaar Van Wersch which was already published in 1992. Three years earlier. In this book the origin of the family Van Werst / Van Weerst / Van Wersch from Warsage is clearly proven. If not by all the possesions they then had.

About 30 km south east of Leipzig there is a little village Wersch.
And according to the Dutch dictionary a werst is an old Russian measure size of 1066,78 meter. Also there is in the Eifel the village Wersch. The town  archive of Aachen wrote:

Zu dem Ortsname Wersch kann ledelich eine Vermutung werden geäussert. In: A. Bach, Deutsche Namenkunde, S.304, ist davon die Rede, das im Ortenamen auch die Lage zu anderen Orten ausgedrückt werden kan, z.b. bei 'Rechtenbach', oder 'Linkenbach' Wers bedeutet mittelniederdeutsch 'links'. Ob der Ortsname "Wersch" sich davon ableitet, kann allerdings nicht mit Sicherheit gesagt werden.
 
 

The present Ferme du Thier Saive in Warsage lies on a hill. At this spot was the original Hof (farm) van Weerst. Around the 12e century there were in Weerst two farms. One of them was owned by knight Arnold van Werst.  By marriage of her ladyship Christine in 1548 with the Lord of Saive (a town in Belgium) the name Ferme du Thier Saive came into existence. "Thier" is an old French word for slope. picture made in 2000

The entrance of the Ferme De Moinerie (the farm of the monks), the second farm in Weerst. The original building was constructed by the Cistarian monks in 1202. Lambert van Werst was the manager under the monks of the Moinerie and was also leading the construction.     picture made in 2000