*conundrum*

n. [ Origin unknown. ] 1. A kind of riddle based upon some fanciful or fantastic resemblance between things quite unlike; a puzzling question, of which the answer is or involves a pun. [ 1913 Webster ]

Or pun ambiguous, or conundrum quaint. J. Philips. [ 1913 Webster ]

2. A question to which only a conjectural answer can be made. [ 1913 Webster ]

Do you think life is long enough to let me speculate on conundrums like that? W. Black. [ 1913 Webster ]