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.