Conundrum

English Etymology Dictionary
conundrum 1596, Oxford University slang for "pedant," also "whim," etc., later (1790) "riddle, puzzle," also spelled quonundrum; the sort of ponderous pseudo-Latin word that was once the height of humor in learned circles.

Merriam-Webster's Collegiate Dictionary, 11th Edition (2003)
conundrum noun Etymology: origin unknown Date: 1645 1. a riddle whose answer is or involves a pun 2. a. a question or problem having only a conjectural answer b. an intricate and difficult problem

Oxford English Reference Dictionary
conundrum
n.
1 a riddle, esp. one with a pun in its answer.
2 a hard or puzzling question.
Etymology: 16th c.: orig. unkn.

Collins COBUILD Advanced Learner\'s English Dictionary
conundrum (conundrums) A conundrum is a problem or puzzle which is difficult or impossible to solve. (FORMAL) ...this theological conundrum of the existence of evil and suffering in a world created by a good God. N-COUNT

English Explanatory Dictionary
conundrum kəˈnʌndrəm n. 1 a riddle, esp. one with a pun in its answer. 2 a hard or puzzling question. [16th c.: orig. unkn.]

Webster's Revised Unabridged Dictionary (1913)
Conundrum \Co*nun"drum\, 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. Or pun ambiguous, or conundrum quaint. --J. Philips. 2. A question to which only a conjectural answer can be made. Do you think life is long enough to let me speculate on conundrums like that? --W. Black.