Page "Capitalization" Paragraph 45

In languages where inflected forms of a word may have extra letters at the start, the capitalized letter may be the initial of the root form rather than the inflected form.

For example, in Irish, in the placename Sliabh na mBan, "( the ) mountain of the women " ( anglicized as Slievenamon ), the word-form written mBan contains the genitive plural of the noun bean, " woman ", mutated after the genitive plural definite article ( i. e. " of the ").

The written B is in fact mute in this form.