related and perhaps of interest: forward.com/articles/9794/the-sabbath-planet This is an unverified source.

Webster makes mention of a connection between seven in various languages and Shabbat (Intro to the American Dictionary of the English Language, Noah Webster, 1828, point 3 of the section, "Change or Loss of Radical Letters," about mid-way through the section).

I edited the question based on what you said. Thank you for your help and answer.

"Grassmann's law, named after its discoverer Hermann Grassmann, is a dissimilatory phonological process in Ancient Greek and Sanskrit which states that if an aspirated consonant is followed by another aspirated consonant in the next syllable, the first one loses the aspiration" --Wikipedia.

Is their any possible insight on the meaning from the root and prefix/suffix of ἐλπίζω