  This is a overview of the genesis of epsilon-delta language in works of
mathematicians of the 19th century. It shows that although the symbols epsilon
and delta were initially introduced in 1823 by Cauchy, no functional
relationship for delta as a function of epsilon was ever specified by Cauchy.
It was only in 1861 that the epsilon-delta method manifested itself to the full
in Weierstrass' definition of a limit. The article gives various
interpretations of these issues later provided by mathematicians.
