On several occasions Paul used the words "Fear & Trembling" (Phil 2:12; 2 Corinthians 7:15; 1 Corinthians 2:3). This is often explained as reverence/respect, but why use both word when "fear" can convey the same message? Did Paul have a specific reason for doing this?
This is likely an example of a hendiadys, a figure of speech where two words are used in a place where one would suffice, for the reason of adding emphasis.
It appears to be a common Hebraism and many see the first such example in Genesis 1 where God "created the heavens and the earth" can stand for "created everything."
Not EVERY construction consisting of, say, two nouns connected with a "and" is a hendiadys, and the decision to identify the figure in a passage has to be made with some thought.