Is there an intentional correlation between Latin letter esh and various summation syntax? So when browsing Unicode characters, I stumbled upon one mysterious case, esh. The upper case Ʃ looks very similar to sigma Σ which is used for summation notation ∑. The lower case ʃ is also suspiciously similar in appearance to the integral ∫ which is also used for sum-related things. I am fairly confident that, since it is a latin character, the connection to sigma is not a coincidence, but did the person who first devised the integral syntax know of the existence of this character, and decide to use a tall s or is it a coincidence because both just happen to be tall s's; one as a lowercase letter the other as a symbol intended to allude to the first letter of the word ~~which brings to mind the symbol which represents it infinitely recursively forever?~~ which it represents?

For the _summation_ symbol $\Sigma$, the use of the capital Greek letter for "s" is due to the use of Latin in Early Modern Europe as universal language; see summa : (mathematics) sum, summary, total.

The first usage is due to Leonhard Euler in 1755; see Institutiones calculi differentialis, page 23 :

> Quemadmodum ad differentiam denotandam vsi sumus signo Δ, ita _summam_ indicabimus signo $Σ$.

Similarly for the long $s$ :

> Leibniz favored the name _calculus summatorius_ and the long letter $\int$ as the symbol. Bernoulli favored the name _calculus integralis_ and the capital letter $I$ as the sign of integration. [...] Leibniz and Johann Bernoulli finally reached a happy compromise, adopting Bernoulli's name "integral calculus," and Leibniz' symbol of integration.