Throughout the medieval period in Europe, large numbers of people traversed the many pilgrimage routes to sacred sites. These multiple journeys had a vast impact on language, as they exposed travellers and their hosts to many vernacular tongues that they would never otherwise have encountered.
Very educated pilgrims could communicate with one another in Latin, then the language of scholarship and the Church, but the need for everyday communication led to the development of glossaries and guides that pilgrims could use on their religious journeys, thus contributing to the standardisation of many languages.
Photo Source: https://historymedieval.com/medieval-pilgrimage-routes-beyond-the-horizon/