It had many cognates in the Germanic languages, such a Old Frisian tam "bridle" and Old Icelandic taumr "bridle, rein, rope." "Team" and its cognates came from the Proto-Germanic taumaz - "the action of drawing or pulling." The English "tow" comes from the same source.
The Proto-Germanic root comes from the Indo-European base deuk-, "pull," which gave Latin the word ducere "pull, lead," source of the English "abduct", "duke", etc.
The word "team" was first used to refer to a group of people working or acting together in the first half of the 16th century. How this came about can be seen in the following quote from Ben Jonson's Barth-olomew Fair: " 'Twere like falling into a whole shire of butter; they had need to be a teeme of Dutchmen, should draw them out."
The OED's earliest citation for the sense of working together is from 1529, and by 1859, Dickens was writing in Tale of Two Cities: "The team had capitulated and returned to their duty."
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