conduit n.

early 15c., "to guide, accompany and show the way," from Latin conductus, past participle of conducere "to lead or bring together; contribute, serve," from assimilated form of com "with, together" (see con-) + ducere "to lead" (from PIE root *deuk- "to lead").

Sense of "to lead, command, direct, manage" is from mid-15c., originally military. General meaning "to direct, manage, act as leader of" is from 1630s; especially of a musical performance (1791).

Meaning "behave in a certain way" is from 1710. In physics, "to carry, convey, transmit," 1740. Related: Conducted; conducting. An earlier verb in the same sense was condyten (c. 1400), which goes with conduit.

To conduct is to lead along, hence to attend with personal supervision; it implies the determination of the main features of administration and the securing of thoroughness in those who carry out the commands; it is used of both large things and small, but generally refers to a definite task, coming to an end or issue: as, to conduct a religious service, a funeral, a campaign. [Century Dictionary]

word-forming element meaning "together, with," sometimes merely intensive; it is the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.