Origin of "Works a treat"

Question

Where does works a treat come from; is it related to sweets? I cannot find any reference to its origin, are there words omitted such as works [like] a treat?

Answer 1

It probably derives from the slang meaning of a treat as used in the following examples:

• a treat, also treato - [late 19C+] wonderfully, extremely, excessively, e.g. that’ll go down a treat.

• In phrases do one a treat (v.) [late 19C+] to suit one absolutely.

(Green Dictionary of Slang)

The extension of the meaning of treat to something that gives pleasures dates back to the 18th century:

• extention Sense of "a treating with food and drink, an entertainment given as a compliment or expression of regard" (1650s) was extended by 1770 to "anything that affords much pleasure."

(Etymonline)

Answer 2

According to a related question/answer, it seems to be a variant usage; both works a treat and works like a treat are used, though (primarily in British usage) the former is far more common (by about two orders of magnitude).

Treat is defined by Merriam-Webster as "an especially unexpected source of joy, delight, or amusement". So while a sweet would work as a treat, it is an example of a treat, but not itself the core meaning. If something works [like] a treat, it works very well, to the delight of the person who set this up.

A quick glance at websites reveals a common use in article headlines which report about some new investment or building project, change in behaviour or similar. It is usually used to positively evaluate the effectiveness of a remedy, behaviour, or project.