"negation" (mainly in pro and con), 1570s, short for L. contra "against" (see contra).
"study," from O.E. cunnan "to know, know how" (see can (v.)).
"swindle," 1889, Amer.Eng., from confidence man (1849), from the many scams in which the victim is induced to hand over money as a token of confidence. Confidence with a sense of "assurance based on insufficient grounds" dates from 1590s. Con also can be a slang or colloquial shortening of several other con- words in English, e.g., from the 19th century, confidant, conundrum, conformist, contract, and from the 20th century, convict, conductor.
"to guide ships," 1626, from Fr. conduire, from L. conducere (see conduce).
/konz/ or /kons/ [LISP, "construct"] A Lisp function which takes an element H and a list T and returns a new list whose head is H and whose tail is T. In Lisp, "cons" is the most fundamental operation for building structures. It actually takes any two objects and returns a "dotted-pair" or two-branched tree with one object hanging from each branch. Because the result of a cons is an object, it can be used to build binary trees of any shape and complexity. [Jargon File]