Sentence:  The other is the maturity and experience of that; if that is our mother tongue, this is our <WSD>father tongue</WSD>, a reserved and select expression, too significant to be heard by the ear, which we must be born again in order to speak. 
Meaning of the word marked with <WSD> tags:  The form of language that is acquired through education and books, as opposed to the dialect one grows up speaking; formal or educated language.