You might want to look at this family in 1880, note the name of their son:

Joseph Duplessis
Home in 1880: 3rd Ward, Plaquemines, Louisiana
Age: 25
Estimated birth year: abt 1855
Birthplace: Louisiana
Relation to head-of-household: Self
Spouse's name: Esther
Father's birthplace: LA
Mother's birthplace: LA
Neighbors: View others on page
Occupation: Laborer
Marital status: Married
Race: Mulatto
Gender: Male

Robert Duplessis 5
Amelie Duplessis 3
Selicourt Duplessis 1