1. A document proofing support apparatus comprising: an input unit configured to receive input of one of at least one proof document and at least one entry document, the proof document including one or more sentences that is to be subjected to a proofing process, the entry document including one or more sentences that is to be subjected to an entry process; an analysis unit configured to perform a morphological analysis, a syntactic analysis and a dependency analysis on each of sentences included in the entry document and generate analysis information including a dependency relation that indicates a semantic connection between words, and to perform a morphological analysis on each of sentences included in the proof document and generate morphological analysis information; a detection unit configured to detect as a possible coined word character string a compound word having a nominal continuation relation by referring to the morphological analysis information, the nominal continuation relation being a relation of two or more consecutive words that can be nouns; a database unit configured to store syntactic information on a correspondence between a sentence included in the entry document and the analysis information; a retrieval unit configured to retrieve whether or not a dependency relation sentence exists, the dependency relation sentence including component words of the possible coined word character string as case elements and having a dependency relation other than the nominal continuation relation between the component words, and to determine the possible coined word character string as a coined word if the dependency relation sentence exists; and a display unit configured to display a message including the coined word.