கடல்
The Tamil word for sea has not moved.
கடல் (kaṭal) is Proto-Dravidian, with clean cognates across the family — Malayalam kadal, Kannada kaṭala. The native sea-vocabulary is unusually full: ஆழி (āḻi) for the deep, திரை (tirai) and அலை (alai) for waves, கரை (karai) for the edge, சேர்ப்பு (cērppu) and புலம்பு (pulampu) for the shore-region. The richness reflects a maritime people. By the early centuries CE Tamils were trading with Rome, Egypt, and Southeast Asia; the words show that lived knowledge.
The classical importance of கடல் is not lexical but structural. The Tolkāppiyam codifies five tiṇai — five landscapes — as the foundation of akam poetics. One of them is neytal, the seashore mode. Its hero is the sēṟppaṉ or pulampaṉ, lord of the shore. Its mood is iruttal, anxious waiting. Its flowers are neytal (the waterlily), puṉṉai (mast-wood), tāḻai (screwpine). Its characteristic scene is the absent lover’s chariot retreating along wet sand. Kuṟuntokai 205 by Ulōchanār is canonical: the heroine watches her lover go, his chariot’s wheels wet with spray from the churning sea, like a swan flying high in rain-cloud sky. The sea is not a backdrop. It is the grammar of the longing itself.
Then Sanskrit arrived, and almost nothing happened.
சமுத்திரம் (samuttiram, from samudra) entered through Puranic and devotional texts, alongside சாகரம், வாரிதி, and the personified sea-deity வருணன். None of these displaced கடல். They specialised. சமுத்திரம் took the cosmic ocean — the seven seas of Puranic geography, the pālkaṭal (sea of milk) of the churning myth. வருணன் took the ritual register. கடல் kept the everyday water.
This is the unusual case. Other major Tamil nature-and-power words moved when Sanskrit arrived: கோ receded to compounds while அரசன் took the king’s chair, தேவன் layered over கடவுள் in religious vocabulary, சந்திரன் added a personified moon-deity that நிலா had never been. The sea did not move. The likely reason is geographical and economic: Tamil sea-life was too continuously lived. Fishermen, merchants, navigators, port-town traders kept the same water named with the same word, generation after generation. There was no Brahminical revolution in fishing the way there was in kingship. The thing stayed; the word stayed.
Modern Tamil’s கடல் is essentially the Sangam word. The compounds proliferate (கடற்கரை, கடற்படை, கடலலை, கடல்மட்டம், கடல் வழித் தளம், கடலோரம்) but the root has not been touched. A modern Tamil child learning the word is learning the same word the Kuṟuntokai poet used to describe the chariot retreating along wet sand. Twenty centuries between them, and no syllable lost.
Etymology phylogeny
Time runs left to right. Solid lines mark descent; dashed lines mark semantic borrowing.