Quiz: Remember the definition of mal de mer?
1640s, "course, direction," from Latin ductus "a leading," past participle of ducere "to lead" (see duke (n.)). Anatomical sense is from 1660s. Meaning "conduit, channel" is 1713; that of "air tube in a structure" is from 1884.
A tubular bodily canal or passage, especially one for carrying a glandular secretion such as bile.