In modern French, negative sentences have a format peculiar among the Romance Languages to French, and with no equivalent in Latin: an awkward and contextually-strange word, pas, is ordinarily required to render a grammatical negative French sentence, like, Je ne comprends pas ce phénomène! ("I don't understand this phenomenon.")
The reason I say it's contextually-strange and awkward is that the ne in the sentence serves the exact same purpose as the pas. Is this an example of fault tolerance through redundancy or something? Why could one not just say "Je ne comprends ce phénomène" ? Where did this pas come from?
The answer is that pas, when used in negation, is an example of a transferred epithet. The transferred epithet is a phenomenon that is actually very common among Indo-European languages (of which French is one).
One meaning of pas is “step” (related to the English word pace), but it can also function as a negative particle when used all alone in common, spoken French, as in, Pas de café, meaning, “there is no coffee”. And while steps and negation seem to be different ideas, these two senses of pas are in fact closely related.
The negating power of pas is thought to come from its historic use in an Old French expression initially used for emphasis – something along the lines of, je ne bois goutte, je ne mange mie, je ne marche pas., literally, (but ungrammatically in Modern French), “I will not drink [even] a drop, I will not eat [even] a bite, I will not walk/march [even] a step.”1 Somehow, the prominence of pas in this emphatic statement of disavowal became as important as (and in the case of pas de café, more important than) the older Latin (and Indo-European) ne, meaning “not”. Hence, the NO-ness of ne got transferred on top of the "stepness" of pas, and now, pas can mean either.
There are a zillion examples of Indo-European transferred epithets, but the coolest one, IMHO, is the transposition of "dryness" with "land-ness". This example manifests in the English word terrain and its myriad of relatives in English, Latin, and Romance Languages. This is because its Latin predecessor, terra, comes from an Indo-European root dealing with drying or dryness, ters-. Ters-, is evident in the English thirst and toast, both clearly associated with dryness.
But before terra there was already an Indo-European root connoting land itself: lendh-. The term terra took on its meaning for “land” or “Earth” because of its use as the word for “dry” in the phrase “dry land”! So ters-, which while initially meaning “dry” came to mean “land” through epithet transference.
While the examples I have provided here both involve Latin, there are many other examples of epithet transference in other branches of Indo-European languages. And although epithet transference is certainly not unique to Indo-European cultures, it is more common.
For Indo-European Roots:
Watkins, Calvert (ed.) The American Heritage Dictionary of Indo-European Roots (New York: Houghton Mifflin Company, 2000).
1. This example graciously provided by E2 user Rudra, to replace my original, weaker example.