Hungarian Notation
Related to sigils is Hungarian notation, a convention for variable-naming that specifies variable type by attaching certain alphabetic prefixes to the variable name. Unlike sigils, however, Hungarian notation provides no information to the compiler; as such, explicit types must be redundantly specified for the variables (unless using a language with type inference). As most standard compilers do not enforce use of the prefixes, this permits omission and also makes code prone to confusion due to accidental erroneous use.
Read more about this topic: Sigil (computer Programming)