1630s, "hidden, occult, mystical," from Late Latin crypticus, from Greek kryptikos "fit for concealing," from kryptos "hidden" (see crypt). Meaning "mysterious, enigmatic" is attested by 1920. Related: Cryptically.
late 14c., "causing doubt, not distinct in character, meaning, or appearance," from doubt (n.) + -ful. From c. 1400 as "of uncertain issue, precarious." From early 15c. as "full of doubt, having doubt, hesitant, wavering." By mid-15c. as "admitting or subject to doubt." Related: Doubtfully; doubtfulness.
Other words that have been used in English in some or all of these senses were doubtous "undetermined" (mid-14c.); doutive "filled with doubt" (late 14c.); douty "ambiguous, enigmatic, obscure" (late 14c.); doubtable (c. 1400); doubtsome (1510s).
1776, from French charade (18c.), probably from Provençal charrado "long talk, chatter," which is of obscure origin, perhaps from charrar "to chatter, gossip," of echoic origin. Compare Italian ciarlare, Spanish charlar "to talk, prattle." The thing itself was originally a verse word-play based on enigmatic descriptions of the words or syllables according to particular rules.
As we have ever made it a Rule to shew our Attention to the Reader, by 'catching the Manners living, as they rise,' as Mr. Pope expresses it, we think ourselves obliged to give Place to the following Specimens of a new Kind of SMALL WIT, which, for some Weeks past, has been the Subject of Conversation in almost every Society, from the Court to the Cottage. The CHARADE is, in fact, a near Relation of the old Rebus. It is usually formed from a Word of two Syllables; the first Syllable is described by the Writer; then the second; they are afterwards united and the whole Word marked out .... [supplement to The Universal Magazine of Knowledge and Pleasure, volumes 58-59, 1776]
Among the examples given are:
My first makes all nature appear of one face;
At the next we find music, and beauty and grace;
And, if this Charade is most easily read,
I think that the third shou'd be thrown at my head.
[The answer is "snow-ball."]
The silent charade, the main modern form of the game, was at first a variant known as dumb charades that adhered to the old pattern, and the performing team acted out all the parts in order before the audience team began to guess.
There is one species of charade which is performed solely by "dumb motions," somewhat resembling the child's game of "trades and professions"; but the acting charade is a much more amusing, and more difficult matter. ["Goldoni, and Modern Italian Comedy," in The Foreign And Colonial Quarterly Review, vol. vi, 1846]
An 1850 book, "Acting Charades," reports that Charades en Action were all the rage in French society, and that "Lately, the game has been introduced into the drawing-rooms of a few mirth-loving Englishmen. Its success has been tremendous." Welsh siarad obviously is a loan-word from French or English, but its meaning of "speak, a talk" is closer to the Provençal original.