I am seeing something called Attic reduplication at least that is what I have heard commentaries, lexicons and Greek grammars say about 1 John 1:1. And to make matters worse I did not remember reduplication from my Biblical Greek studies in seminary. I am not familiar with Attic and do not have any Attic resources in my library. In 1 John 1:1, I can see the base word ἀκηκόαμεν is derived from ἀκούω. I base this on my study of grammars and interlinears. It is parsed as perfect, active, indicative. I know that some verbs beginning in a vowel reduplicate the entire first syllable. Based on Mounce’s grammar, A.T. Robertson's grammar and LSJ my understanding is that when a verb starts with a vowel, the ἀ would get longer, but the initial vowel plus consonant (ἀκ) would not repeat. Is that the case? How can I use Logos Bible Software to determine if this is in fact Attic reduplication? I asked a friend of mine who took Greek in seminary and he said it was a strange case and could not explain it further. Would this resource in Logos be helpful to my question? English–Greek Dictionary: A Vocabulary of the Attic Language by S. C. Woodhouse https://www.logos.com/product/15748/english-greek-dictionary-a-vocabulary-of-the-attic-language
I went through each of these factbook entries. https://beta.app.logos.com/search?kind=factbook&layout=one&q=%22Attic+reduplication%22&resources=allResources&source=searchPanel&syntax=v2
https://beta.app.logos.com/search?kind=all&layout=one&q=%22Attic+reduplication%22&resources=allResources&source=searchPanel&syntax=v2 got 14 hits
https://beta.app.logos.com/search?case=ignore&engine=lexical&form=all&kind=books&layout=one&q=%22Attic+reduplication%22+NEAR+John&ref=default&resources=allResources&source=searchPanel&syntax=v2&view=book got 0 hits
https://beta.app.logos.com/search?case=ignore&engine=lexical&form=all&kind=books&layout=one&q=%22Attic%22+NEAR+%221+John%22&ref=default&resources=allResources&source=searchPanel&syntax=v2&view=book Got 2 hits
https://beta.app.logos.com/search?kind=all&layout=one&q=%22Attic%22+AND+%22+1+John%22&resources=allResources&source=searchPanel&syntax=v2 Got 53 hits but when restricted to 1 John 1 only got 3 hits.
ieul-article-p41_3.pdf This is something I read as well.