Source : Webster's Revised Unabridged Dictionary (1913)

Penetralia \Pen`e*tra"li*a\, n. pl. [L., fr. penetralis
   penetrating, internal. See {Penetrate}.]
   1. The recesses, or innermost parts, of any thing or place,
      especially of a temple or palace.

   2. Hidden things or secrets; privacy; sanctuary; as, the
      sacred penetralia of the home.

Source : WordNet®

penetralia
     n : the innermost parts
     [also: {penetralium} (pl)]