The line "he descended into hell" in Latin says "he descended ad infernum," which translates as "to the nether regions". It's a reference to the "preaching to the spirits in prison" (the righteous who died before the resurrection, in other words) mentioned in 1 Pt 3:19.
Interesting - thanks for the clarification. I had to memorize the Nicene Creed for a guitar mass when I was attending the Episcopal church in Caracas and I still get them mixed up.