Charlie is a name. Their habit of naming is after their father, their brother who died young, or their grandfather's name. Girls are often named after their grandmothers (in memory of their mother), or the names of sisters who died young, or the names of their grandmothers. Or the name of a parent's best friend, or the name of a godmother or godfather.
In short, it is to commemorate relatives or use the names of outstanding great people.