During the conflict, Republicans undertook a rewriting of toponymy, a phenomenon that Joan Tort, Professor of Geography at the University of Barcelona, describes as common in revolutionary processes. This initiative primarily affected names with religious connotations, such as Sant Feliu de Guíxols, which became simply Guíxols, or those linked to seigneurial domains, like Molins de Rei, renamed as Molins de Llobregat.

The initial changes, driven by popular committees in a context of "agitation and misgovernance" after the coup d'état of July 18, 1936, were carried out without clear regulation. It was not until October 1936 that the Republican Generalitat intervened, establishing that town councils had to approve the changes, which subsequently required validation from the Consell de la Generalitat.

Criteria for the new names included the suppression of "Sant" or "Santa," the incorporation of geographical elements (such as Puigsacalm for Sant Privat d'en Bas), or historical references (such as Empori for Sant Pere Pescador). A notable example of inventiveness and improvisation was the change from Sant Boi de Llobregat to Vilaboi, a name that, according to Tort, "sounds like an invention" and reflects the lack of planning in many cases.

With the victory of the national side in April 1939, the 124 name changes were declared null. Many municipalities reverted to their previous names, but some were Castilianized by the Franco regime. Thus, Vilaboi returned to being Sant Boi de Llobregat, but was later transformed into San Baudilio de Llobregat. Similarly, Sant Cugat del Vallès, which had been Pins del Vallès, became San Cucufate del Vallés.

This often little-known episode is part of the history of the war's losers and was a profound but short-lived change, followed by a long period of silence during Francoism. Despite this, some municipalities, after Franco's death, officially decided to recover the names adopted during the Republican era, such as Bellaguarda or Vilanova del Vallès.