When language used in a document is plain in itself, but is unmeaning in reference to existing facts, evidence may be given to show that it was used in a peculiar sense.
     Illustration
     A sells to B, by deed, "my house in Calcutta".
     A had no house in Calcutta, but it appears that he had a house at Howrah, of which B had been in possession since the execution of the deed.
     These facts may be proved to show that the deed related to the house at Howrah.