Where does “I'mn't” come from?

I'mn't (English) comes from English I’m, from English I, from Old French i, from Latin hīc, from Latin heic, from Latin hic, from Proto-Italic hek(e), from Proto-Indo-European gʰi-ḱe — resin, gum; to say, speak.

Ancestry of “I'mn't”, step by step

StepLanguageWordMeaning
1EnglishI’m
2EnglishIThe speaker or writer, referred to as the...
3Old Frenchithere
4Latinhīcthis; these in the plural
5Latinheic
6Latinhicthis; these in the plural
7Proto-Italichek(e)
8Proto-Indo-Europeangʰi-ḱethis, here
9Proto-Indo-EuropeanḱeDeictic particle, here; Post-positional...
10Middle Englishkyt
11Germankittputty certain kinds of cement used for fixing e.g. window panes
12Old High Germankuti
13Proto-West Germanickwidugum, resin
14Proto-Germanickweduzresin
15Proto-Indo-Europeangʷet-resin, gum; to say, speak
Every word from Proto-Indo-European gʷet-