In linguistics, the excessive case indicates a transformation away from a state. This case completes the "going in, being in, going out" paradigm:

[translative] - transform into a state. "Appointed a minister", nimitettiin ministeriksi.
[essive] - existence in a state. "Stays a minister", pysyy ministerinä.
[excessive] - transform away from a state. "Fired from the minister's job", sai potkut ministerintä.

Observe the similarity to the [illative], [inessive] and [elative] cases (into, in, out from the inside something) for physical locations. This is an actual "hole in our thinking" we're unaware of. Notice how the state - "job" - has to explicitly stated; "fired from a minister" is incorrect.

Only some Eastern dialects of [Finnish], like [Karelian] and [Savo], use this case. Its case ending is -nta/ntä depending on [vowel harmony]. Because its use is so limited geographically, it has not entered standard Finnish. Speakers from other areas will not recognize it. The origin of the ending may be explained as -na + -ta → -nta, where the [essive] "in a role" is prefixed with an [ablative] "from", creating the concept "from a role". Notice that the old Finnish ablative -ta has been transformed into a [partitive], its role overtaken by the modern Finnish ablative -lta.

For example, huollettava "[dependant]" → Kuol (pois) huollettavanta "Died (away) from being a dependant". This cannot really be expressed other than in an [analytic] fashion, i.e. "Died, and is no longer a dependant", in standard [Finnish] or English. As a case, it's added to the [adjective]s, and it works with the [translative case] in the most logically beautiful way: Hyväntä ystäväntä muuttui hän pahimmaksi vihamieheksi. "From being a good friend, he changed into a worst enemy."

Source: http://www.kotus.fi/julkaisut/ikkunat/2003/kielii2003_7.shtml

excessive case (idea)