Etymology
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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.
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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"]
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pre-treat (v.)

also pretreat, "to treat beforehand," by 1912, originally in reference to water purification, from pre- "before" + treat (v.). Related: Pre-treated; pre-treating; pre-treatment.

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treatment (n.)
1560s, "conduct or behavior toward someone or something," from treat (v.) + -ment. In the medical sense, it is first recorded 1744.
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untreatable (adj.)
late 14c., "unmanageable," from un- (1) "not" + treatable (see treat (v.)). In medicine, of diseases, conditions, etc., by 1865.
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maltreat (v.)

"to treat ill, abuse," 1708, from French maltraiter, or formed in English from mal- + treat (v.). Related: Maltreated; maltreating.

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mistreat (v.)

"treat badly, abuse," late 15c., mistreten, from see mis- (1) + treat (v.). Related: Mistreated; mistreating.

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treatise (n.)
early 14c., from Anglo-French tretiz (mid-13c.), contracted from Old French traitis "treatise, account," from traitier "deal with; set forth in speech or writing" (see treat (v.)).
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treatable (adj.)
c. 1300, "amenable to reason," from Anglo-French tretable, Old French traitable, and in part from treat (v.) + -able. Of wounds, diseases, etc., "receptive to treatment," early 15c.
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tractable (adj.)
"manageable," early 15c., from Latin tractabilis "that may be touched or handled, workable, tangible, manageable," figuratively, "pliant," from tractare "to handle, manage" (see treat (v.)). Related: Tractability.
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