Back and book etymology

I know, that most of you will think, that it is absurd, but please read to the end.

Sorry for my English

Introductory:

When I read the Ostrog Bible I saw, that in the OCS the verb "to unbend a book" was used (instead of "to open a book").

At the first onset I thought about a knee, because in Russian we use that verb with this noun.

Whereupon I thought, that the English/German word knee/Knie is consonant to the first part of the OCS word "kniga".

Thereupon I thought, that the Old Slavonic laguage has a borrowed words, where "ga" is a suffix (for an example, French cheval "a horse" -> Old Slavonic chevlaga/chevluga "an old horse").

Thereupon I thought, that if someone doesn't have a table he put his "kniga" on a "knee".

Thereupon I thought, that the English verb "unbend" translates to German "geradebiegen".

Thereupon I thought about Bogen (bow), Bucht (bight) and Buch (book).

Thereupon I thought, that a knee bore little comparison to a book spine.

Thereupon I got an answer, that "The English use of 'spine' for that part of a book is modern, only from the early 20th century. Before that, this part of the book was generally known as the 'back' "

Question: Does the English word "back" somehow relate to "book"? I can not imagine a book without a back.

The official etymology:

back: from Proto-Germanic *baką possibly from Proto-Indo-European *bʰogo (literally “bending”);
book: from Proto-Germanic *bōks or from Proto-Germanic *bōk

Solution 1:

No.

back (n.)
Old English bæc "back," from Proto-Germanic *bakam

book (n.)
Old English boc "book, writing, written document," generally referred (despite phonetic difficulties) to Proto-Germanic *bōk(ō)-, from *bokiz "beech"

– both from Etymonline.com

They are superficially similar in English, having a single syllable b–k, but come from different roots.

The resource etymonline.com is recommended, especially if you do not have access to the OED.