stranding (n.)

A term used in some GRAMMARS to refer to an ELEMENT which is left unattached after it has been MOVED out of a CONSTRUCTION, or after the rest of the construction has been moved. For example, a PREPOSITION is commonly left stranded, after the NOUN PHRASE within the prepositional phrase has been moved, as in Who did you give the book to?; the AUXILIARY verb did is stranded after the ELLIPSIS of the second CLAUSE in He asked her to arrive before six, but she didn’t.