Etymology of ending "-keit" in relation to ending "-heit"

Question

It appears that in general adjectives can be nominalized by adding the suffix -heit, which however changes to -keit in case the adjective already has been formed by use of a suffix, like -bar,*-ig*, -lich, -sam.

As stated in etymology-on-line for the English suffix -hood, and by Kluge's Etymological Dictionary of the German Language, -heit has its origin in an independent noun (hade? in old English), the same root occurs in the German adjective heiter and has cognates in other Indo-European languages.

Is there any etymological evidence (earlier forms of German) showing how -keit developed from -heit?

Answer 1

The etymology of the ending "-keit" is rather complicated, as we have influences from a different pronunciation in High German vs. Low German dialects here.

Example "Ewigkeit":

Up until today the adjective ending "-ig" is pronounced differently in northern and southern regions. See for example "ewig":

• Pronunciation in standard German: [ˈeːvɪç] (same a ch in "Ich").
• Pronunciation in Swabia: [ˈeːvɪk] (same as ck in "dick").

Now, for "ewig" the pronunciation in Old High German was different from today, as we can see from the Middle High German spelling ewic, or ewik. The adjective was then nominalized using the common suffix "-heit" to give Ewic-heit which then became Ewikeit by dropping the h on pronunciation.

Only later the now missing g from "ewig" was reintroduced to become "Ewigkeit". Until today this added g curiously is pronounced as "ch" in standard German: [ˈeːvɪçkaɪ̯t]. Interestingly in many German dialects "Ewigkeit" is still pronounced as [ˈeːvɪkaɪ̯t], i.e. the g introduced from spelling is ignored.

Other variants

This phenomenon happened to many adjectives, including other adjectives that did not end on -ic leading to an independent additional suffix -keit, and even another independent suffix -igkeit was introduced (e.g. "Gerechtigkeit", "Farbigkeit"). In other cases the -keit suffix was dropped again for -heit (e.g. rein > Reinic-heit > Reinekeit > Reinheit), or both suffixes coexisted at times (Frommheit - Frömmigkeit, Munterheit - Munterkeit). On top of all this confusion it may also be that when pronounced as ch the ending may also be spelt with ch (vrœlīc-heit > Fröhlichkeit).

For a concise insight into the etymology of "-keit" and many more examples see:

• Grimms Wörterbuch der deutschen Sprache

Indo-European etymology

In Old High German -heit already is present, sharing it's roots with the adjective heiter, and the Old Saxonian hēd, Old English hād, Gothic haidus, and Old Norsk heiðr. All these, and Old Indian kētúḥ, or Latin caelum probably go back to a common Indo-European root (s)kāi-.^DWDS

Summary

In summary we can see that the suffix -keit shares the same etymology with -heit but it's spelling changed over time.

Answer 2

Maybe this explains it better for you.

-keit is a result of a wrong segmentation of two Middle High German suffixes -ec (-ig) and -heit: -ec-heit was interpreted as -e-keit.

-keit seems to be the equivalent to the English -ness

The reference for -heit is here

Answer 3

I think a connection between -heit and heiter is erroneous. Semantically there is no connection at all. In Latin adjectives can have a noun with the suffix -tas/tatis as in sanus, adj. and sanitas, genitive sani-tat-is. I assume that this suffix derives from status/u:s meaning state or condition. Sanitas is the state or condition of being sanus.

And I think that German -heit is connected with Latin -tat-i that might give tait and heit if t is dropped and h is used to show that there was a plosive. So Gesundheit or Krankheit simply means the state of being well or sick and it has nothing to do with "heiter" (cheerful). I consider -keit just a variant of -heit in certain special positions.