Origins
The word 'emit' was borrowed directly from Latin 'Δmittere' in the early seventeenth century.βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ The Latin verb combines 'Δ-' (a variant of 'ex-,' meaning 'out') with 'mittere' (to send, to let go, to release). To emit is to send something outward β light from a star, heat from a flame, sound from a throat, gases from a volcano.
Latin 'mittere' is one of the most prolific verb roots in the English language, though its ultimate origin is obscure. It may descend from a Proto-Italic form *mett-, but no clear Proto-Indo-European ancestor has been established. Whatever its origin, 'mittere' generated an enormous family of English words through its various prefixed forms.
The compound verbs of 'mittere' read like a catalogue of fundamental human actions. 'Admittere' (ad- + mittere, to send to) gave English 'admit.' 'Committere' (com- + mittere, to send together, to entrust) gave 'commit.' 'DΔ«mittere' (to send away) gave 'dismiss.' 'Intermittere' (to send between, to pause) gave 'intermit' and 'intermittent.' 'Omittere' (to let go, to send past) gave 'omit.' 'Permittere' (to let through) gave 'permit.' 'PrΕmittere' (to send forward, to pledge) gave 'promise.' 'Remittere' (to send back) gave 'remit' and 'remission.' 'Submittere' (to send under) gave 'submit.' 'TrΔnsmittere' (to send across) gave 'transmit.'
French Influence
The past participle of 'mittere' is 'missus' (sent), which produced its own family. 'Missio' (a sending) gave English 'mission' β originally a religious sending, as when missionaries were sent to convert distant peoples. 'Missilis' (that which can be thrown or sent) gave 'missile.' Through Vulgar Latin and Old French, 'missus' evolved into 'message' (something sent) and 'messenger' (one who carries what is sent).
In modern English, 'emit' is most commonly found in scientific and environmental contexts. Stars emit light and radiation. Radioactive materials emit particles. Engines emit exhaust gases. The noun 'emission' has become central to climate science and policy: 'carbon emissions,' 'greenhouse gas emissions,' 'zero-emission vehicles.' The phrase 'carbon emissions' would have been unintelligible before the twentieth century, yet it is now one of the most consequential compound terms in global politics.
The financial sense of 'emit' β to issue currency, bonds, or decrees β preserves an older usage. In the eighteenth century, colonial governments in America 'emitted' paper money, and the U.S. Constitution (Article I, Section 10) prohibits states from 'emitting bills of credit.' This usage treats money as something sent out into circulation, which is precisely what 'emit' means.
Latin Roots
The word also has a quieter, more literary register. A person may 'emit a sigh' or 'emit a cry.' These uses preserve the Latin sense of releasing something from within β letting go of what has been contained. A sigh emitted is breath that has been held; a cry emitted is sound that has been suppressed.
The journey of 'emit' from Latin bureaucratic and military vocabulary (sending out troops, issuing edicts) through scientific terminology (sending out radiation, particles, light) to environmental policy (carbon emissions, emissions targets) traces the expansion of human concern from the political to the physical to the planetary. The word has not changed its meaning β it still means 'to send out' β but what we send out, and what we worry about sending out, has changed enormously.