Perhaps what all hypocoristic forms have in common is an atmosphere of familiarity.    From Wordnik.com.  [VERBATIM: The Language Quarterly Vol VII No 2] Reference

Linguistic boffins have no problems with a statement like "dim. of BAUGH, from W bychan, hypocoristic form of bach little.".    From Wordnik.com.  [VERBATIM: The Language Quarterly Vol XVII No 4] Reference

Besides phonetic and morphological arbitrariness, there is an unpredictable element in the semantics of hypocoristic forms, at least in Australia.    From Wordnik.com.  [VERBATIM: The Language Quarterly Vol VII No 2] Reference

It could be a hypocoristic or baby-talk form of hysterical, or it might be from the imitative word hiss; or perhaps it is a variant of another dialect term, jesse, meaning a ` severe scolding, 'which is probably from a Biblical allusion.    From Wordnik.com.  [VERBATIM: The Language Quarterly Vol XIX No 1] Reference

Simple names appear to have been more frequent in early times, but some are in reality hypocoristic, i. e., abbreviated forms of compound names as Saul (asked), David (beloved) Nathan (he gave), etc., which were probably combined with a Divine name, Yah or 'El. Simple Names.    From Wordnik.com.  [The Catholic Encyclopedia, Volume 10: Mass Music-Newman] Reference

&c., most of these being "hypocoristic affixes," corresponding in a measure to modern pet-names.    From Wordnik.com.  [Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 1 "Austria, Lower" to "Bacon"] Reference

hypocoristic A pet name, such as Willie or honey.    From Wordnik.com.  [Mind Hacks: Hypocoristic] Reference