Phrasefinder puts "card sharp" (or "-sharper") as the slightly earlier usage, with an 1859 citation for "card-sharper" and "card-sharp" in both Britain and in the US, while "card-shark" is cited to 1893 in the US.
Card sharps who cheat or perform tricks use methods to keep control of the order of the cards or sometimes to control one specific card. Many of these methods employ sleight of hand. Essential skills are false shuffles and false cuts that appear to mix the deck but actually leave the cards in the same order. More advanced techniques include culling (manipulating desired cards to the top or bottom of the deck), and stacking (putting desired cards in position to be dealt).
Dealing the cards can also be manipulated. Once a desired card or cards are located they can be controlled and dealt as the cheater wishes. This is called a false dealing; if a card is dealt from the bottom it is called bottom dealing and if it is second from the top it is called second dealing. Two cards could be dealt as one or the second card from the bottom could be dealt, hence the Greek deal and double deals. Dealing may also be done from the middle of the deck, known as the middle deal or center deal, but is almost always performed as a display of skill rather than actual cheating.
"blackleg". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.) https://www.oed.com/search/dictionary/?q=blackleg
Harper, Douglas (2001). "Online Etymology Dictionary search results". EtymOnline.com. entries "shark" & "sharp". Archived from the original on 2007-07-13. Retrieved 2007-07-08. – gives the negative meaning only, for both http://www.etymonline.com/
Hawkins, Joyce M.; Allen, Robert, eds. (1991). The Oxford Encyclopedic English Dictionary. New York: Clarendon Press. p. 1334. ISBN 0-19-861248-6. – gives only the negative meaning for both; labels negative verb "to sharp" archaic. 0-19-861248-6
Chapman, Robert L., ed. (1983). New Dictionary of American Slang. New York: Harper & Row. p. 380. – gives both positive and negative meanings for both "shark" and "sharp", labels them synonymous in this context, and indicates that positive sense of "shark" arose much later than the negative meaning, and later than it did for "sharp"
Partridge, Eric (1983). Origins: A Short Etymological Dictionary of Modern English. New York: Greenwich House. p. 614. ISBN 0-517-41425-2. – gives only negative meaning for "shark", and gives "sharper" as synonymous, without addressing the shorter form "sharp" 0-517-41425-2
McKechnie, Jean L., ed. (1971). Webster's New Twentieth Century Dictionary of the English Language (Unabridged ed.). New York: Simon & Schuster. pp. 274, 1668. ISBN 0-671-41819-X. – gives both meanings for both terms and even for the obsolete "sharker", but provides only the swindler definition for "card sharp" and both definitions for the "card shark" version, thus contradicting itself at the "sharp" entry 0-671-41819-X
Harper, Douglas (2001). "Online Etymology Dictionary search results". EtymOnline.com. entries "shark" & "sharp". Archived from the original on 2007-07-13. Retrieved 2007-07-08. – gives the negative meaning only, for both http://www.etymonline.com/
Chapman, Robert L., ed. (1983). New Dictionary of American Slang. New York: Harper & Row. p. 380. – gives both positive and negative meanings for both "shark" and "sharp", labels them synonymous in this context, and indicates that positive sense of "shark" arose much later than the negative meaning, and later than it did for "sharp"
Onions, C. T., ed. (1994). The Oxford Dictionary of English Etymology. New York: Oxford at the Clarendon Press. p. 817. ISBN 0-19-861112-9. – gives only the negative meaning for both "shark" and "sharp" 0-19-861112-9
Weekley, Ernest; Scott, Anne, eds. (1911). New Gem Dictionary of the English Language. London: Collins. p. 418. – current around time that "shark" gained a positive sense, gives only negative meaning for both
Hawkins, Joyce M.; Allen, Robert, eds. (1991). The Oxford Encyclopedic English Dictionary. New York: Clarendon Press. p. 1334. ISBN 0-19-861248-6. – gives only the negative meaning for both; labels negative verb "to sharp" archaic. 0-19-861248-6
Chapman, Robert L., ed. (1983). New Dictionary of American Slang. New York: Harper & Row. p. 380. – gives both positive and negative meanings for both "shark" and "sharp", labels them synonymous in this context, and indicates that positive sense of "shark" arose much later than the negative meaning, and later than it did for "sharp"
McKechnie, Jean L., ed. (1971). Webster's New Twentieth Century Dictionary of the English Language (Unabridged ed.). New York: Simon & Schuster. pp. 274, 1668. ISBN 0-671-41819-X. – gives both meanings for both terms and even for the obsolete "sharker", but provides only the swindler definition for "card sharp" and both definitions for the "card shark" version, thus contradicting itself at the "sharp" entry 0-671-41819-X
Kipfer, Barabara Ann; Princeton Language Institute, eds. (1999). Roget's 21st Century Thesaurus in Dictionary Form (2nd ed.). New York: Dell Publishing. pp. 306, 786. ISBN 0-440-23513-8. – gives both meanings for both 0-440-23513-8
"Search results". Dictionary.Reference com Unabridged (v1.1 ed.). Lexico Publishing Group. 2007. "sharp" dfn. 36 & 37, and "shark" dfn. 2-1 & 2-2. Archived from the original on 2016-03-05. Retrieved 2007-07-08. – gives both meanings for both, with negative meaning being primary for both, positive meanings informal http://dictionary.reference.com/
McKechnie, Jean L., ed. (1971). Webster's New Twentieth Century Dictionary of the English Language (Unabridged ed.). New York: Simon & Schuster. pp. 274, 1668. ISBN 0-671-41819-X. – gives both meanings for both terms and even for the obsolete "sharker", but provides only the swindler definition for "card sharp" and both definitions for the "card shark" version, thus contradicting itself at the "sharp" entry 0-671-41819-X
Soukhanov, Anne H., ed. (1994). Webster's II: New Riverside Dictionary. Boston: Riverside Pub. Co. p. 1072. ISBN 0-395-33957-X. – gives both for "shark", only negative for "sharp" and "sharper" 0-395-33957-X
Guralnik, David B., ed. (1982). Webster's New World Dictionary of the American Language (Revised ed.). New York: Warner Books. p. 547. ISBN 0-446-31450-1. – gives both for "shark", only negative for "sharp" 0-446-31450-1
Chapman, Robert L., ed. (1983). New Dictionary of American Slang. New York: Harper & Row. p. 380. – gives both positive and negative meanings for both "shark" and "sharp", labels them synonymous in this context, and indicates that positive sense of "shark" arose much later than the negative meaning, and later than it did for "sharp"
"American Heritage Dictionary of the English language". Bartleby.com (online 4th ed.). Houghton Mifflin. 2006. "sharp" dfn. noun 3, and "shark" dfn. noun 2. Archived from the original on 2008-02-20. Retrieved 2007-07-08. – gives both meanings for both, with positive being primary for "sharp" but negative for "shark" http://www.bartleby.com/61/
Martin, Gary. "The Meaning and Origin of the Expression: Card-sharp", The Phrase Finder. Retrieved 30 Sept. 2021. https://www.phrases.org.uk/meanings/card-sharp.html
Maskelyne, John Nevil (1983). Sharps and Flats. Casino Press. ISBN 0-87019-049-0. 0-87019-049-0
Johnson, Karl (2005). The Magician and the Cardsharp: The Search for America's Greatest Sleight-of-hand Artist. Henry Holt and Co. ISBN 0-8050-7406-6. 0-8050-7406-6