1570s, "language, speech, mode of speech," especially "form of speech of a region or group, idiom of a locality or class" as distinguished from the general accepted literary language, also "one of a number of related modes of speech regarded as descended from a common origin," from French dialecte, from Latin dialectus "local language, way of speaking, conversation," from Greek dialektos "talk, conversation, speech;" also "the language of a country, dialect," from dialegesthai "converse with each other, discuss, argue," from dia "across, between" (see dia-) + legein "speak" from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')").
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.
"style of speech," early 15c., from Latin locutionem (nominative locutio) "a speaking, speech, discourse; way of speaking," noun of action from past-participle stem of loqui "to speak," from PIE root *tolkw- "to speak." Related: Locutionary.