Let's take John, Fred and Paul and consider the affectionate diminutive (AD) forms of their names. John becomes Johnny, Fred becomes Freddie, Paul becomes Paulie. Formalizing the transformation:
- Trailing consonant doubled: J+, F+, P-
- ie as a trailing vowel pack for the AD form: J-, F+, P+
- y as a trailing vowel for the AD form: J+, F-, P-
I understand that this is how English works, different names get transformed differently. But is there a rule that tells which pattern a particular name would follow, or you simply have to memorize all the names and their proper AD forms?