Where does the saying cream of the crop come from? I know it means the best of the lot but I couldn't find anything on how it came to be.
I haven't heard it myself, although I have heard of "cream" being used to refer to as the best. After looking it up, I discovered that someone makes this statement:
Cream is the richest part of the milk and rises to the top. The noun ‘cream’ has been used to mean the best of any collective entity since the 16th century. ‘Cream of the market’ was an early expression using ‘cream’ figuratively and John Ray used the phrase ‘ the cream of the jest’ in his 1678 collection of English proverbs.
Those are pretty early quotes, but is that where "cream of the crop" originated from? Reading on:
‘Cream of the crop’ was undoubtedly adopted for its alliterative appeal and probably borrowed from the French ‘la crème de la crème,’ the cream of the cream, the best of the best, which was well-known in English by about 1800. But exactly when and where the ‘cream of the crop’ first came into use is unknown.
It probably came from French, although this is not absolutely definite.
Cream is the part of milk that concentrates most of the fat. As such, it's often considered the best part of milk, and by extension the best part of anything. This is reinforced by the fact that the cream is what floats to the top. The word for cream can metaphorically mean the best part of something in many European languages. I don't think there's any etymological connection here, rather shared cultural referents (milk as a common foodstuff, valorisation of fat, positive connotation of top over bottom).
There is an earlier expression, crème de la crème (often spelled creme de la creme), which is a borrowing from French (where it means, literally, cream of the cream). In both languages, the expression means metaphorically the best of the best, i.e. the very best. The expression crème de la crème is rather uncommon in French, where I think the use of crème to mean best has declined. The French expression may have had additional appeal in English because French evoked sophistication and the ruling class. In the 20th century, the use of creme de la creme declined (possibly due to the reduced exposure to and influence of French in English-speaking countries), though it has seen a recent revival.
cream of the crop,crème de la crème,creme de la creme http://ngrams.googlelabs.com/chart?content=cream%20of%20the%20crop%2Ccr%C3%A8me%20de%20la%20cr%C3%A8me%2Ccreme%20de%20la%20creme&corpus=0&smoothing=3&year_start=1800&year_end=2000