text: what is the etymology of the word "manifold'? in mathematics, a manifold is a certain type of topological space. it also stands for a car component (e.g. exhaust manifold). why is this word used for such disparate things? what is its origin? manifold is a germanic/old english word that means, simply, "many folds."  in today's language, it generally means many folds, forms, or features.  i would say the two uses of the word you mentioned are both perfectly reasonable.  exhaust manifolds are structures that have multiple inlets/outlets (hence, many features).  in topology, manifolds are, in general, surfaces with many features.