2.5 Stem isolation. A result of shortening a name can introduce ambiguity in what the original full spelling of the name might have been. Syllable truncation can mean that the first syllable of the name is all that is left. Thus the name Brad might be a shortening of Bradley, Bradford, or even Brady. Other masculine forms are: Al, Gil, Jay, Phil, Ty and Wil. Sometimes though the full name belongs to people of a particulary gender, as in these examples, it could as well come from names of either gender, e.g. Chris, Jo, Kay and Dee.
This variety of derivation results in a single syllable name; often appropriate for adding a diminutive suffix to. Hence, we have Joey, Chrissy and Willy. There are therefore some pet forms for which the stem isolate itself is not attested: Ellie, Lanny.
This particular kind of derivation was quite popular among the early Germanic tribes so that a case could be made for some of these unattested names having been formed in that time period. More likely, however, is the possiblity that the direct process of forming the hypocorism itself was preserved into the modern period, without the requirement that there be a stem isolate attested.