Aspergillus is a genus of fungus/mould which is very common - A. niger is the black furry stuff you get in fridges, and is very tenacious. it's called Aspergillus as its form rather resembles that of an aspergillum, which is used to sprinkly water on people during Mass (in catholicism - dunno about other denominations). basically, imagine a round headed lollipop, and that's yer aspergillus.
the word "aspergillum" comes from a Latin word meaning to sprinkle. for example, The Asperges in the Latin Mass:
"Asperges me Domine hyssopo et mundabor,
lavabis me et super nivem dealbabor."
which means: "sprinkle me, Lord, with hyssop and I shall be cleansed; thou shalt wash me, and I shall be made whiter than snow."
(i know various asperges in church music - i've sung "asperges me" by michael haydn, which is very sprightly).
see? isn't it handy to have your very own pet microbiologist, ex-catholic, choral singer on hand?