Aha! Bhante @sujato, I found an article on topic! This is what you might have been looking for! CATUPATISAMBHIDA by Bhikkhu Kusalaguṇa
Many thanks to @knotty36 and @cdpatton for their replies. I really appreciate your comments on a matter that is not particularly clear to me.
The reason I was seeing 辯 as oral skill is that 辯 can translate less ambiguously for patibhāna…in context 辯無礙解 (as fourth member of the list) 
無滯之言說即辯也。辯 indicates unobstructed speech. 辯 [biàn] also resembles bhāna phonetically…a point which shouldn’t be taken lightly.
Honestly I was just following what I could grok from Ding Fubao’s Foxue Da Cidian. In context of term 四無礙辯, 辯 (辨) meaning bhid is not impossible…but the risk of there being some (very murky) link to patibhāna was why I was not certain. However, I was called to this thread for the Indic phonology, not the Chinese hehe, so I am content to let such opaque matters as 解 and 辯 rest for now. 
[edit: I have also since reread Ding Fubao’s statement: 是為諸菩薩說法之智辯，故約於意業而謂為解，謂為智，約於口業而謂為辯。 and I conclude that 辯 does in fact have the sense of discriminating knowledge (of speech) here, and of patibhāna elsewhere. Many thanks to @cdpatton @knotty36 for showing me this]
I meant “glossed” in a very loose sense of some dictionaries giving the alternative translation, 四無礙智 to explain 四無礙解.
无碍 is a bit of a mystery, it may come from the " saṃ" in " saṃvida", which has the idiomatic sense of “thoroughly” here (implying conjunction or completeness) . Thoroughly known in the case of samvida. We also see this in Pali verbal form paṭisaṃvidita.
Personally, I would not try to explain the meaning of the prefix sam in the word paṭisambhidā due to its weak attestation. But this is what the Pāli commentaries have said:
Vibhaṅga Aṭṭhakathā defines it as “paṭisambhidāti pabhedā”, “paṭisambhidā means category”.
The Pācittiyādiyojanapāḷi, on the other hand, defines ‘paṭisambhidā’ as “Atthādīsu pati visuṃ sambhijjatīti paṭisambhidā, paññā”. (loosely)paṭisambhidā is the wisdom that analyses separately into categories as attha, etc’.
The Pāli tradition introduces a new verb, sambhijjati, which we did not see in this context in the canon. It takes us down the root of defining paṭisambhidā as “knowledge of the categories” or, the wisdom which knows the categories.
This Pāli commentarial way of thinking does not appear to show up in the Northern commentaries or post-canonical literature.