Title self explains: Is the symbol for set membership $\in$ derived from greek letter $\epsilon$? What is their historical relationship? Obviously the letter must be older, since greek alphabet is extremely old. Paul Halmos Naive Set theory, page 2, second paragraph (equivalently page 2 lines 8-11)
This version of the Greek letter epsilon is so often used to denote belonging that its use to denote anything else is almost prohibited. Most authors relegate $\in$ to its set-theoretic use forever and use $\epsilon$ when they need the fifth letter of the Greek alphabet.
In the comments of this answer is found a discussion, but not in the form of answer. Also this site seems more appropriate than Math.SE.