Can anyone tell me the origin of "as cool as a cucumber"?

Question

Can anyone tell me the origin of  "as cool as a cucumber"?

Answer

http://www.phrases.org.uk/meanings/38500.html

First recorded in John Gay's Poems, New Song on New Similies, 1732

It's a mix of meanings - a cucumber feels cool (low temperature) when you touch it.  Cool also means 'calm', which is the meaning of this idiomatic expression.

Answer

It means  to be calm in any situation.