Superstition

Friday the 13th is a good day to look at the word "superstition". Back in the 1500s, English speakers liked to borrow words from Latin to sound learned, and because of the Protestant Reformation they were always on the lookout for ways to slag off the Catholic Church. With "superstition", they got a two-for-one deal. It is derived from the Latin word superstitiōnem, the noun of action derived from superstāre (to stand upon or over).
It is thought that the etymological meaning of this is ‘standing over a thing in amazement or awe’. When it was first used in English, it was with the sense "Unreasoning awe or fear of something unknown, mysterious, or imaginary, esp. in connection with religion; religious belief or practice founded upon fear or ignorance", and the quotations from the time will give you an idea of the tenor of the debate, if you could call it that:

a1538   T. Starkey Dial. Pole & Lupset  Their [the monks'] solitary life which hath brought forth with little profit to the public state, much superstycyon.

1547  J. Griffiths Two Bks. Homilies Other kinds of papistical superstitions‥as of Beads, of Lady Psalters and Rosaries.

1549  H. Latimer Serm. Ploughers Where the Devyll is residente‥up with all superstition and Idolatrie, sensing,‥holye water, and newe service of mens inventing.

This was obviously a much more loaded term than the one we use now for touching a rabbit's foot for good luck! 

For an explanation of why we say "thirteenth" instead of "threeteenth", click here.

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