The word hypocoristic is a technical term which is applied to words which are also less technically called “pet names”. Pet names are names of the type which are used to address and refer to other people in such a way as to indicate familiarity and fondness.
Hypocoristics are particularly often used of, and to, children. And many of them are also diminutives, indicating in some way or other relatively small size.
One obvious linguistic mechanism which can be used in English for constructing a hypocoristic out of a particular given name is abbreviation, as with Jennifer being abbreviated to Jen. But you cannot just chop off pieces of words at random to achieve this effect. There are rules concerning how to go about this. Any name which consists of only one syllable cannot readily be shortened. Within the constraints set by the English language, speakers cannot make names such as May, Guy, Judd or Lee any shorter than they already are.
But even many other longer names do not offer a great deal of choice when it comes to abbreviation either. The only established way of abbreviating a name such as Peter is surely to convert it into Pete. David can give us Dave, but surely nothing much else, except that there is also the possibility that it can be lengthened to Davey, using the diminutive ending -y, as also with Jenny.
But other two-syllable words can offer additional possibilities. Names can be shortened at the beginning, as with Anthony becoming Tony or, more usually, at the end as with Richard becoming Rich.
English also has a good number of very traditional hypocoristic names, some of them centuries old and based on rhyming, such as Dick, and Bill, and female rhyming forms such as Nell from Helen. Many younger people, however, now seem to be avoiding these long-established forms, maybe because they just don’t know about them, in favour of simple shortenings such as Rich and Will.
It is also possible for names to change their vowels in order to achieve a hypocoristic effect, as with James giving us Jim, and Michael producing Mick as well as Mike.
Particularly interesting from a linguistic point of view is the availability of alternative abbreviations for the same name. Patricia, for instance, can give us Pat, Trish or Trisha. Isabelle can be abbreviated as Izzy as well as Bella.
William can lose either its beginning or its end: in addition to Bill and Will, it can also become, as often in Ireland and among Catholics, Liam. Alexander is sometimes Alex and sometimes Xander, with the latter generally being pronounced as if it was written with a Z at the beginning.
There are also other minor processes which can be used to produce pet-name forms, such as the substitution of L for R as in the derivation of Molly from Mary or Margaret or Martha. But Margaret can also be turned into Meg, or rhymingly, into Peg.
Gerry can be abbreviated to Ger, but only if you have the sort of Scottish or Irish accent where “Ger” rhymes with “hair”.
Christine and Christopher can both appear as Chris, and Alex can be derived from both Alexander and Alexandra.
ANTHONY
The English-language given name Anthony was originally the Roman family name Antonius, as borne by the well-known historical figure Marcus Antonius, known in English as Mark Antony. It was originally borrowed into English as Antony, but the H was added later in the mistaken belief that the name had originally come from Ancient Greek anthos “flower”.