What is Cis
Cis as a label was invented in the 1990's and popularized in the 2010's as a means to distinguish between people who are and aren't trans. Cis- was coined from the latin word meaning "on the same side as." Much like the modifier hetero-, cis- is not a slur but rather a descriptor for linguistic clarity.
Much like how the modifier 'biological' before the word parent acts as a helpful clarification in medical contexts without diminishing adoptive parents paternal roles, cis can be helpful to describe medical or social distinctions between people who are and aren't trans much more clearly than words that assign value like 'biological' or 'normal.'