Etymology fail!
From Wiktionary:
Etymology 1
From Latin cis (“on the same side”).
Adjective
(biology) Having two mutations on two genes on the same chromosome of a homologous pair.
(cytology) Of the side of the Golgi apparatus nearer to the endoplasmic reticulum.
(chemistry) In (or constituting, forming, or describing) a double bond in which the greater radical on both ends is on the same side of the bond.
the cis effect is the labilization of ligands which are cis to certain other ligands
https://en.wiktionary.org/wiki/cis#Etymology_1