Origins of the word ‘Click.’

1581, of imitative origin; perhaps French or Dutch.
Probably developed earlier as a way to corral horses,
in expressing reprimand or sympathy, or produced in audible kissing.

Also, any of various stop consonants, found in Khoisan and as borrowings in southern Bantu languages, that are produced by the suction of air into the mouth.

The figurative sense of "fit together" first recorded in 1915.

Used as Canadian/U.S/European slang for kilometer,
sometimes spelled klik or klikken.

In computing, pressing and releasing a button on a mouse or other pointing device to cause an event in virtual space. Distinguished from “right-click;” the regular usage implies the left button.



Source: http://dictionary.reference.com/browse/click