Meaning:
Something that makes no sense.
Origin:
This line originates in Shakespeare's Comedy of Errors, 1590:
DROMIO OF SYRACUSE:
Was there ever any man thus beaten out of season,
-> When in the why and the wherefore is neither rhyme nor reason?
-> When in the why and the wherefore is neither rhyme nor reason?
The bard must have liked the line as he used it again in As You Like It, 1600:
ROSALIND:
But are you so much in love as your rhymes speak?
ORLANDO:
Neither rhyme nor reason can express how much.