Why is the ninth month called September?
early 15c., from Middle French complication, from Latin complicationem (nominative complicatio), noun of action from past participle stem of complicare "to fold together, fold up, roll up," from com- "together" (see com-) + plicare "to fold, weave" (see ply (v.1)). Meaning "something that complicates" first recorded 1903.
complication com·pli·ca·tion (kŏm'plĭ-kā'shən)
A pathological process or event occurring during a disease that is not an essential part of the disease; it may result from the disease or from independent causes.