Still, most of us associate Mondays with phrases like blue Monday. That names a Monday considered depressing or trying especially because of the return to work and routine after a weekend.

Blue Mondays are one thing, but we found two Monday-related illnesses that spell plenty of trouble. Monday fever, also known as byssinosis (byssos means "linen garment" in Latin) is "an occupational respiratory disease associated with the inhalation of cotton, flax, or hemp dust." Characterized by chronic bronchitis and sometimes complicated by emphysema or asthma, Monday fever (or "mill fever") leads to irreversible lung disease.

Just as the health of workers afflicted with byssinosis worsens when they report to the mill Monday morning, so too does the health of horses suffering from Monday disease take a turn for the worse at the start of their workweek. The formal name of Monday disease—azoturia—recognizes the excess of nitrogenous substances in the horse's urine (azote means "nitrogen"); the informal name has its origin in the fact that the equine stiffening and muscular paralysis, profuse sweating, and collapse occurs when the horses are returned to work after being heavily fed and inadequately exercised for several days.