treat (v.)

c. 1300, "negotiate, bargain, deal with," from Old French traitier "deal with, act toward; set forth (in speech or writing)" (12c.), from Latin tractare "manage, handle, deal with, conduct oneself toward," originally "drag about, tug, haul, pull violently," frequentative of trahere (past participle tractus) "to pull, draw" (see tract (n.1)).

Meaning "to entertain with food and drink without expense to the recipient by way of compliment or kindness (or bribery)" is recorded from c. 1500. Sense of "deal with, handle, or develop in speech or writing" (early 14c.) led to the use in medicine "to attempt to heal or cure, to manage in the application of remedies" (1781). Related: Treated; treating.

treat (n.)

late 14c., "action of discussing terms," from treat (v.). 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."

What treat can we have now? If we were to treat ourselves now—that is, to have dainties a little above our means, it would be selfish and wicked. It is the very little more that we allow ourselves beyond what the actual poor can get at that makes what I call a treat .... But now—what I mean by the word—we never do make much of ourselves. None but the poor can do it. I do not mean the veriest poor of all, but persons as we were, just above poverty. [Lamb, "Old China"]

Definitions of treat
treat (v.)
interact in a certain way;
Synonyms: handle / do by
treat (v.)
subject to a process or treatment, with the aim of readying for some purpose, improving, or remedying a condition;
treat the water so it can be drunk
treat the lawn with chemicals
treat an oil spill
Synonyms: process
treat (v.)
provide treatment for;
The patient must be treated right away or she will die
The doctor treated my broken leg
Synonyms: care for
treat (v.)
act on verbally or in some form of artistic expression;
The new book treats the history of China
Synonyms: cover / handle / plow / deal / address
treat (v.)
provide with a gift or entertainment;
Grandmother always treated us to the circus
I like to treat myself to a day at a spa when I am depressed
treat (v.)
provide with choice or abundant food or drink;
Don't worry about the expensive wine--I'm treating
She treated her houseguests with good food every night
Synonyms: regale
treat (v.)
engage in negotiations in order to reach an agreement;
they had to treat with the King
treat (v.)
regard or consider in a specific way;
I treated his advances as a joke
treat (n.)
something considered choice to eat;
Synonyms: dainty / delicacy / goody / kickshaw
treat (n.)
an occurrence that causes special pleasure or delight;