The term "basso profondo" refers to a male vocalist who sings in the range an octave lower than a normal bass part. It came to be colloquially referred to as "Russian bass", because of its popularity among Slavic composers. I have always had a deep (pardon the pun) admiration for these vocalists, which is why I chose to share this with you.
Here's a recording of We Bow Down Before Your Cross, composed by Pyotr Goncharov, which includes basso profondo. It might be a bit long for some of your attention spans, but I find it unbelievably beautiful.