This duplication of deities, the result of the final fusion of kindred tribes who had long lived apart, would account for the appearance of Janus beside Jupiter, and of Diana or Jana beside Juno in the Roman religion. At least this appears to be a more probable theory than the opinion, which has found favour with some modern scholars, that Janus was originally nothing but the god of doors. That a deity of his dignity and importance, whom the Romans revered as a god of gods and the father of his people, should have started in life as a humble, though doubtless respectable, doorkeeper appears very unlikely. So lofty an end hardly consorts with so lowly a beginning. It is more probable that the door (_janua_) got its name from Janus than that he got his name from it. This view is strengthened by a consideration of the word _janua_ itself. The regular word for door is the same in all the languages of the Aryan family from India to Ireland. It is _dur_ in Sanscrit, _thura_ in Greek, _tür_ in German, _door_ in English, _dorus_ in old Irish, and _foris_ in Latin. Yet besides this ordinary name for door, which the Latins shared with all their Aryan brethren, they had also the name _janua,_ to which there is no corresponding term in any Indo-European speech. The word has the appearance of being an adjectival form derived from the noun _Janus._ I conjecture that it may have been customary to set up an image or symbol of Janus at the principal door of the house in order to place the entrance under the protection of the great god. A door thus guarded might be known as a _janua foris,_ that is, a Januan door, and the phrase might in time be abridged into _janua,_ the noun _foris_ being understood but not expressed. From this to the use of _janua_ to designate a door in general, whether guarded by an image of Janus or not, would be an easy and natural transition.