

The expression appeared in Jonathan Swift's My Lady's Lamentation (1728).

In 1609 Thomas Dekker used the term in The Gull’s Hornbook ‘when at a new play you take up the twelve-penny room next the stage, (because the Lords and you may seem to be haile fellow wel-met) there draw forth this booke, read alowd, laugh alowd, and play the Antickes, that all the garlicke mouthd stinkards may cry out, Away with the fool.'

"Well met" appears to have been added to the phrase in the 16th century to intensify its friendliness, and derives from the concept of "good to meet you", and also from the meaning of "meet" as something literally the right size for a given situation. The Oxford English Dictionary (OED) gives a 1589 quotation for this phrase as a friendly greeting, and quotations for the related phrase "hail fellow", a greeting that apparently dates to medieval times. "Hail fellow well met" is an English idiom used when referring to a person whose behavior is hearty, friendly, and congenial, in the affirmative sense.
