Gadget

A gadget is a small tool such as a machine that has a particular function, but is often thought of as a novelty.

Gadgets are sometimes referred to as gizmos.

According to the Oxford English Dictionary, there is anecdotal evidence for the use of "gadget" as a placeholder name for a technical item whose precise name one can't remember since the 1850s; with Robert Brown's 1886 book Spunyarn and Spindrift, A sailor boy’s log of a voyage out and home in a China tea-clipper containing the earliest known usage in print.

The October 1918 issue of Notes and Queries contains a multi-article entry on the word "gadget" (12 S. iv.

The 'jigger' or short-rest used in billiards is also often called a 'gadget'; and the name has been applied by local platelayers to the 'gauge' used to test the accuracy of their work.
In fact, to borrow from present-day Army slang, 'gadget' is applied to 'any old thing.'

In the software industry, "Gadget" refers to computer programs that provide services without needing an independent application to be launched for each one, but instead run in an environment that manages multiple gadgets.

The earliest documented use of the term gadget in context of software engineering was in 1985 by the developers of AmigaOS, the operating system of the Amiga computers (intuition.library and also later gadtools.library).