A lot of names with the letter R in them have developed short forms in the past which leave out the R e.g.
Christopher has the short form
Kit,
Sarah became
Sally,
Bridget becomes
Biddy (not Briddy) and
Frances became
Fanny (not Franny) although this isn't used much in Britain now because
Fanny has developed as a slang term for the female genitals!
Also in modern times the Z seems to replace the R sound e.g. Karen/Caroline becomes Kaz/Caz,
Barry becomes Baz,
Sharon becomes Shaz or Shazza as a nickname.
Rosey.