What is "interrelatedness"? Do the Pali suttas teach about "interrelatedness"?
Here is the literal answer to your question: https://suttacentral.net/search?query=interrelatedness
I assume by your quotes that you are asking the objective question whether any popular translator has used that literal word as a translation of a specific Pali word or phrase of concept. The link above should provide your answer.
If you are asking a different question if the concept conveyed by the imperfect word “interrelatedness” exists in the Pali canon and what the Buddha had to say about it... well I’ll let you rephrase the question I guess.
In this context the word was used to refer to dependent arising:
Dependent arising is the interrelatedness of dharmas
IMO the word paṭiccasamuppāda can be analyzed as:
- Paṭicca [ger. of pacceti, paṭi+i; cp. BSk. pratītya] grounded on, on account of, concerning, because (with acc.)
- conjunction, closer connection = with, along, together.
- yutta: yoked, connected > saṃyutta: bound together, grouped.
- vasati: to live > saṃvasati: to live together with
- completeness, or accentuation of the meaning = thoroughly, quite, fully, perfectly. It often equals pa- with which it gets combined in sampa-.
- bodhi: awakening > sambodhi: complete awakening
- jāna: knowing > sampajāna: knowing thoroughly.
- Uppāda coming into existence, appearance, birth
... so literally or etmymologically (beware some people don't like taking etymology as meaning) it means something like, "coming into existence with".
It's not much of a stretch to translate that as "interconnected" or "interrelated".
Wikipedia lists several English translations for paṭiccasamuppāda:
Paticca-samuppada, (Pali: “dependent origination”) Sanskrit pratitya-samutpada, the chain, or law, of dependent origination, or the chain of causation—a fundamental concept of Buddhism describing the causes of suffering (dukkha; Sanskrit duhkha) and the course of events that lead a being through rebirth, old age, and death.
Existence is seen as an interrelated flux of phenomenal events, material and psychical, without any real, permanent, independent existence of their own. These events happen in a series, one interrelating group of events producing another. The series is usually described as a chain of 12 links (nidanas, “causes”), though some texts abridge these to 10, 9, 5, or 3. [etc.]
Indra's net (also called Indra's jewels or Indra's pearls, Sanskrit Indrajāla) is a metaphor used to illustrate the concepts of Śūnyatā (emptiness), pratītyasamutpāda (dependent origination), and interpenetration in Buddhist philosophy.
The metaphor was developed by the Mahayana school in the 3rd century Avatamsaka Sutra and later by the Huayan school between the 6th and 8th centuries.
... though that's off-topic since you asked for Pali suttas (only).
Still I think it's evidence that some people are going to understand or translate, or have seen translations of, "dependent arising" as some "interrelatedness" -- perhaps of dhammas in general, and/or perhaps of nidanas in particular.
I don't think it's the most precise translation, which may be why you don't recognise it.