I first heard the term cis six years ago from trans friends and have identified as a queer cisman since that time. Cis or cisgendered describes people who are not transgendered, who still identify, more or less, with the gender they were assigned at birth. It comes from the Latin word ‘cis’ which means ‘on the near side of’ and is the opposite of the Latin word ‘trans’ which means ‘across’ or ‘on the far side of’. So, for example, the piece of land on the far side of the Romanian forest was called Transylvania (sylvan means woods) and the piece of ancient Gaul that was on the near side of the Alps (relative to Rome) was called Cisalpine Gaul.
Having a word that specifies people who are not trans in a way that does not also imply normalcy or authenticity (as options like ‘regular man’ or ‘bio-woman’ do) works to strip the language of some of its implicit biases and allows more generic terms like ‘man’ and ‘woman’ to be understood as trans inclusive (even if they don’t include everyone in the genderqueer middle of the gender spectrum). I also really appreciate having a way to identify my gender that is true to my experience and also signals my awareness of non-cisgender experience.