Surnames were often quite common (due to a relatively closed society) and first names were usually suggested by the church resulting in the duplication of names in small communities. To avoid confusion "nicknames" were formalized and often the person and their family were more known by that "nickname" than by their official identity. It is like a formalised and acceptable "nickname". "Dit" would mean "known as". This practise is not specific to Quebec. It is also common in other rural communities. Usually the family and individual are known only by their "dit" ....name except for official use.