Origins
The word 'tremor' is one of those rare terms whose meaning has remained essentially stable across two millennia of linguistic change. Latin 'tremor' meant 'a trembling' or 'a shaking,' and Modern English 'tremor' means exactly the same thing. The word's semantic stability reflects the visceral, physical nature of the phenomenon it describes — trembling is a universal bodily experience that requires no cultural translation.
Latin 'tremor' is a noun formed from the verb 'tremere' (to tremble, to quake, to shiver), which descends from the Proto-Indo-European root *trem-, meaning 'to tremble.' Greek inherited the same root as 'tremein' (τρέμειν, to tremble), and the correspondence between Latin and Greek forms is exact. The root appears to be onomatopoetic in origin — the repeated 'tr' sound mimics the rapid, repetitive vibration of trembling, much as 'buzz' mimics a buzzing sound.
The word entered English in the late fourteenth century, borrowed directly from Latin with no French intermediary (though French 'tremblement' comes from the same root through a different derivational path — via the verb 'trembler,' which English also borrowed as 'tremble'). The existence of both 'tremor' (directly from Latin) and 'tremble' (through French) in English is a typical doublet: two words from the same ultimate source that arrived by different routes and settled into different grammatical roles — 'tremor' as noun, 'tremble' as verb.
Modern Usage
In modern usage, 'tremor' has three primary domains. The geological sense — an earthquake tremor, or a minor earthquake — is perhaps the most common in news media. Seismologists distinguish between the main shock of an earthquake and the smaller 'tremors' (foreshocks and aftershocks) that precede and follow it. A 'tremor' in this sense is typically a minor seismic event, while a full 'earthquake' implies significant magnitude.
The medical sense refers to involuntary, rhythmic muscle contractions that cause shaking movements. Tremors are a symptom of numerous neurological conditions, most famously Parkinson's disease, where a resting tremor (shaking that occurs when the muscles are relaxed) is one of the cardinal diagnostic signs. Essential tremor, a condition affecting hand steadiness, is one of the most common movement disorders, affecting approximately 10 million Americans. The Latin medical phrase 'delirium tremens' (trembling delirium) — a severe form of alcohol withdrawal involving shaking, confusion, and hallucinations — preserves 'tremens' as a present participle.
The emotional and figurative sense — 'a tremor of excitement,' 'a tremor ran through the crowd' — extends the physical metaphor to psychological states. The connection between emotion and physical trembling is physiologically real: intense fear, excitement, or cold trigger involuntary muscle contractions, and languages worldwide describe emotional states in terms of shaking.
Latin Roots
The broader word family includes 'tremble' (the French-derived verb), 'tremendous' (from Latin 'tremendus,' meaning 'to be trembled at,' hence 'awe-inspiring' and later simply 'very large'), 'tremulous' (from Latin 'tremulus,' meaning 'shaking, quivering'), and the musical term 'tremolo' (from Italian, a rapid repetition of a note or alternation between two notes that creates a trembling effect).
The semantic history of 'tremendous' deserves special note. It originally meant 'such as to cause trembling' — terrifying, awe-inspiring, dreadful. Over time, it underwent 'semantic bleaching,' losing its emotional specificity and becoming a general intensifier meaning 'very large' or 'very great.' When someone says 'a tremendous success,' they no longer mean a success that makes you tremble — they simply mean a very large success. This kind of semantic erosion is common with emotion words, which tend to lose their visceral force through frequent casual use.
From PIE *trem- through Latin 'tremere' to modern English, 'tremor' has maintained an almost perfect continuity of meaning. The ground trembles, the body trembles, the voice trembles, the heart trembles — and the word for this universal experience of involuntary shaking has itself remained steady across millennia of linguistic change.