The word "honeykins" uses two suffixes to make it more endearing: "-kin" and "-s".

**[-kin][1]** is an English suffix that was used in the olden days to form diminutive forms of nouns. There are still [several dozen words in the language][2] that were formed using this suffix. The more known are *pumpkin, catkin, napkin,* the less known are *ladykin, pannikin*.

It has a curious etymology, let me quote from Wiktionary:

[![enter image description here][3]][3]

See - it's Germanic in origin: compare with German "[Mädchen][4]", "a girl". It is composed of the root "Madg", "female servant", and the diminutive suffix "-chen". 

Another interesting bit, from "A History of British Surnames" by Richard McKinley, [page 100][5]:

[![enter image description here][6]][6]

It turns out Richard Daw**kin**s has this suffix too! Live and learn.

The linguistic term for a diminutive, endearing calling name is **[hypocorism][7]**.

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According to Wiktionary, [the suffix **-s** has 5 meanings][8], and one of them is hypocoristic:

> Diminutive suffix:   
*Babs; moms; pops; homes; Toots*

In the "Cambridge Grammar of the English Language" by Huddleston and Pullum, both "-kin" and "-s" are mentioned in Unit 5.2.1 "Evaluative morphology: Diminutives". 


  [1]: https://en.wiktionary.org/wiki/-kin
  [2]: https://en.wiktionary.org/wiki/Category:English_words_suffixed_with_-kin
  [3]: https://i.sstatic.net/lK6mA.png
  [4]: https://en.wiktionary.org/wiki/M%C3%A4dchen
  [5]: https://books.google.ru/books?id=gcOOAwAAQBAJ&lpg=PA100&ots=hA8ddm6c7S&dq=hypochoristic%20%22kin%22&hl=ru&pg=PA100#v=onepage&q&f=false
  [6]: https://i.sstatic.net/jPrRS.png
  [7]: https://en.wikipedia.org/wiki/Hypocorism
  [8]: https://en.wiktionary.org/wiki/-s#Etymology_5