Familiar phrase, anyone? Who was this? Heidegger? Kant? Why am I not finding it via search engine? Is my grammar off somehow?
“Das Ding an sich” is Kant.
This one looks like Heidegger. “Dingheit der Dinge”.
I’m not familiar with the phrase, but my Google-Fu suggests that it’s spelled “dinges.”
What’s that mean in English? 'Cause after reading that phrase in German, I’m getting that earwig of a Chuck Berry song My Ding-A-Ling in my head now. (Which is a song about a bell, of course.)
Grammatically correct it would be Dingliche Dingheit des Dinges (thingly thingishness of the thing) or possibly in plural: Dingliche Dingheit der Dinge (thingly thingishness of things) but there is no Google hit for either of these exact phrase so it seems we have been spared this as a philosophical term of art. Yet.
Dingens mentioned is not an official German word. It is occasionally encountered as as a genitive form of Dings, a German equivalent of thingumajig, but we can probably discount this as part of a serious usage - the Sprachebene of Dings militates against the Sprachebene of Dingliche Dinglichkeit.
For the sake of completeness, I venture to mention that Dingens would be the genitive of the gerund of a theoretically possible verb *dingen (to thing [sic]) but this verb is not used.
Translating the phrase to English isn’t easy, since the words used in the phrase were made up by the writer to express the philosophical notions he had in mind; you could roughly translate “dingliche Dingheit des Dinges” (yes, Mindfield, that’s “Dinges,” not “Dingens”) as “the thing-like thing-ness of the thing.” What this means is up to you, but it obviously refers to Kant’s “Ding an sich” (thing as such), which, as far as I understand it, means that existing things exist in their own right, no matter if they are perceived by others or not.
So that’s where ‘dingus’ comes from!
“Thingly thingishness of the thing”? Deep. That’s, like, a five-bowl insight right there. Tell me when you know what it is to be a rock, but not to roll.
The rock is square, dude. Think about it. I haven’t.
It’s just a box of rain. I don’t know who put it there.
Is it a thingy-do or a thingy-don’t?
I prefer Advanced Dingheit des Dingens. 
Not being very familiar with the the works of either Heidegger or Kant, how close is this concept to Object Permanence? or does it refer to concepts and conditions as well as (or instead of) objects?
I might be able to understand, but I’m too lazy to read the books…
To summarize their work:
Immanuel Kant was a real pissant who was very rarely stable.
Heidegger, Heidegger was a boozy beggar who could think you under the table.