A large number of Prakrit words (Middle Indo Aryan languages) have (as Wiktionary describes) 'pleonastic suffixes' such as -ka, -lla-, -Da, etc.
What exactly is a "pleonastic suffix" and what is the origin of these suffixes, and why did they come into use so suddenly?
A pleonastic suffix is one which is redundant in that the basic meaning of the word is exactly the same but the extension has a certain effect that could be emphatic, poetic, or diminutive. It is quite common for these suffixes to be added to words with an already diminutive meaning.
It is unlikely that they came into use suddenly, as noted they are related to Sanskrit diminutives, and our body of knowledge about Sanskrit and Prakrit comes from strictly literary media which intentionally eschewed many of the tendencies of vernacular Indo-Aryan. The etyma for many of the “rude” words in New Indo Aryan are obscure and poorly attested, for example the common IA verb for “to fart” has not been identified in Prakrit. Certainly it must have been widely used in the past however. Languages which have been in continuous contact with Indo-Aryan such as Pashto also have parallel suffixes.
Hardev Bahri offers a detailed overview of the origins of the specific pleonastic/diminutive suffixes in Indo-Aryan in his thesis on the phonology of the Awankari dialect, Lahndi Phonology (Chapter 4): https://archive.org/details/Lahndi_Phonology/page/19/mode/2up
As noted, some of them have multiple origins and have been reinforced by contact with Iranian languages.
