Duct: A tube, pipe or passageway. A conduit, often in a building.
Descended from the latin ductus meaning leading, itself the noun form of duco meaning I lead, because a duct leads something through a channel. It wasn’t until English from the 1660s that it came to have the anatomical sense, and that of a conduit came about in 1713, and as an air tube not until 1884.
But where does the word itself derive from? We need to look further back. And what else is related to duct?
Duco also gives us the word duke, a leader, and is descended ultimately from the Proto Indo-European *dewk- meaning to lead or to pull or draw. *Dewk is also the origin of such words as the Welsh dwyn meaning to steal, via the celtic *duk-o- meaning to carry.
Duct in English occurs as a component of many other words. Induct comes from the latin induco, a past passive participle of duco, carrying the sense of “being led”. Conduct derives from latin too, the verb conduco being to lead together, and is also the origin of the word conduit.
There are latin prefixes that can be affixed to duct – ab gives abduco meaning I lead away – and English abduct. De– leads to deduct and deduce from deduco meaning I bring away. Deduct differs from similar words such as subtract and abduct in that abduct came to mean by force whereas deduct means to take away a part of something. Deduce came to be taking away something in the sense of coming to a realization. Subtract comes from the latin subtraho “to pull out from under” – itself from sub “under” and traho “I drag”.
Duco also gives us the English word educate. The latin educo, from ex-duco, ex being the prefix meaning out or away, such as exterior or extract (similarly from traho). Educo meant to lead away, and in that way came to be the word for teaching.
Being very versatile duco also provides the English word induce, using the latin prefix in- meaning conveniently “in”. Induco means I lead in, often in the sense of to bring an object into somewhere, likely a court or a home. And figuratively it came to mean to bring an idea into a discussion, or to convince and persuade someone of something, hence the English “induce”.
Similarly duco gives us introduce. The latin verb introduco meaning I lead in, from the prefix intro-, also means to originate something and bring something forward. In English it is introduce that carries the physical sense, while induce has retained largely only the mental sense.
Seduce is another word derived from duco. Se- the latin prefix means astray, so to seduce someone is to lead them astray. The sexual sense is English, originating in the 16th century.
sources: www.etymonline.com, wiktionary.org, Oxford dictionary of Word Origins Second Edition.