filth fly
n.— «Filth flies. Which is another name for a typical housefly, but they occur in such large numbers here due to poor sanitary conditions in the cities.» —“Wasilla man fights pests as contractor for military” by S.J. Komarnitsky Anchorage Daily News (Ak.) July 6, 2005. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...
Cat hair may be something you brush off, but cat hair is also a slang term that means “money.” In the same way, cat beer isn’t alcoholic — some people use cat beer as a joking term for “milk.” And imagine walking on a...