All of the sources I checked agree that this expression refers to someone inexperienced and/or naïve. My favorite explanation of the origin is from American farm language that refers to a foal or calf that is literally still wet behind the ears from the birth.

I had always accepted that this idiom is used when referring to something that is too small to make a difference. I was surprised when I looked up the origin. The Phrase Finder writes that it was used in the Bible, Isaiah 40:15, “Behold the nations are as a drop of a bucket, and are counted as the small dust of the balance…” “A “drop in the bucket’ is the predecessor of “drop in the ocean,” which was first published in The Edinburgh Weekly Journal in July 1802.

This means to miss going to somewhere that you were expected, and is commonly used to mean not going to work or school. There are various ideas of where the expression originated. The Urban Dictionary thinks it is probably from the Dutch word hoekje, which is their term for a hide and seek game that had players searching for a hidden object. Schoolchildren began using “hooky” to mean skipping school in the nineteenth century. Another less likely possibility is that the term originated with the verb hook, which means “to steal.”

The expression means to meet an expected standard, but is often used in the negative, such as, “The performance did not cut the mustard.” There are several theories on the origin, but The Phrase Finder believes it came from “the heat and piquancy of mustard and the zest and energy of people’s behavior.” “Cutting” has long been used to mean “exhibiting” as in “cutting a fine figure.” Therefore, cutting the mustard is “…an alternative way of saying ‘exhibiting one’s high standards’.” The Iowa State Reporter used the expression ‘Cut the Mustard’ in 1897.

The actual phrase is cater corner, and cater is from the French word “quatre” (four).  It means directly and diagonally across. It was Americanized by replacing the unfamiliar “cater” with the familiar “catty” and then “kitty.”  Phrases.org explains replacing an unfamiliar word such as cater with a familiar one is called “folk etymology.”

Yahoo Answers says the distinct point in the hairline in the center of the forehead was called “widow’s peak” from the belief that it was an omen of early widowhood. The sharp point of hair has also been associated with villains such as Count Dracula.