Transmit is Latin trans, "across, beyond," plus mittere, "to send" — to send across. Both halves are among the most productive Latin elements in English: trans- gives transfer, translate, transport and transparent, while mittere gives mission, admit, permit, submit, commit and missile.
English took the word about 1400, and its transparency is typical of directly borrowed Latin. Where a French borrowing has usually been worn smooth — so that nobody sees the parts in charge or chief — a Latin borrowing usually keeps its prefix and root visible, which is why long Latinate English words are easier to parse than short native ones once you know a dozen prefixes. There was also an alternative English verb transmiss, formed from the Latin past-participle stem by way of Old French, which did not survive.
transmit (v.) "send over, onward, or along; cause to pass or go to another person or place," c. 1400, transmitten , from Latin transmittere "send across, cause to go across, transfer, pass on," from trans "across, beyond" (see trans- ) + mittere "to release, let go; send, throw" (see mission ). Figuratively, "convey, communicate to another" (1620s). Related: Transmitted ; transmitting . The obsolete alternative verb transmiss , transmis e (Middle English transmisen ) is from transmis- , the past-participle stem of the equivalent Old French verb. also from c. 1400
transmit came in through Latin, and its spelling follows that family's conventions.
How that family writes these sounds
| a prefix you can hear on the front | pre-, post-, sub-, trans-, inter-, ex-, re-, de-, ab-, ob-predict, transmit, interject, obstruct |
What gives it away on the page
| pre-, post-, sub-, trans-, inter-, ex-, re-, de-, ab-, ob- | Latin prepositions doing duty as prefixes.predict, transmit, interject, obstruct |