Don't cut off your nose to spite your face. -- Mid 14th century French Proverb
This is apparently associated with legends of women disfiguring themselves to protect their chastity. According to wikipedia, one of the most famous stories is that of Saint Ebba of the monastery of Coldingham. She heard that the vikings were coming and cut off her nose and upper lip to make herself unappealing, then urged the other nuns to do the same. Apparently the vikings were so disgusted that they burned the monastery with the nuns inside, so no happy ending there.
The spite part is apparently from the Middle Ages, when cutting off someone's nose was a common act of revenge or punishment.
Beware the ides of March.
This is from Shakespeare's Julius Caesar. The ides of March just means March 15th, because the Roman calendar was arranged around three named days: the Kalends (1st day of the month), the nones (the 7th day in March, May, July, and October; the 5th in the other months), and the ides (the 15th day in March, May, July, and October; the 13th in the other months). The idea that the ides were dangerous was apparently Shakespeare's invention.
Jack of all trades, master of none.
'Jack' was a common name in English, and is used here to mean the common man. Interestingly, the saying wasn't negative to begin with, and the 'master of none' part was added later. 'Jack' referred to someone at the lower end of the social tree, someone not educated, a cad, or a knave in the Middle Ages. In the 16th century people used a disparaging Latin term Johannes factotum (Johnny do-it-all) instead. (Yay, another Latin insult to add to my arsenal!)
According to Phrases.org, the name of Jack was also added to lots of different objects which in some way took the place of a man. Here is a list from the site:
Want to know more? Check out the links below.Smoke-jack (a roasting spit)
Jack-plane (a basic carpenter's plane)
Jack-screw (a lifting winch)
Jack-frame (a carpenter's sawing horse)
Boot-jack (for pulling off boots)
Jack-engine (a miner's winch)
Jack-file (a coarse file)