நிலம்
நிலம் is the ground in every sense Tamil will allow it to be.
The word is Proto-Dravidian, cognate across the family — Telugu nēla, Malayalam nilaṁ, Kannada nela — all meaning the same thing. The likely root is நில் (nil), to stand, to abide. நிலம் is that-which-stands, the abider. The ground stays put while everything moves over it.
நிலம் (nilam) is the deepest native land-word. மண் (maṇ) is the soil, the substance, the physical stuff. நாடு (nāṭu) is country in the political sense, homeland, jurisdiction. புலம் (pulam) is the field, the tract, the poetic patch. ஞாலம் (ñālam) was the older Tamil cosmic-world word, the planet. Each had its register.
The most consequential fact about நிலம் in Sangam Tamil is not lexical, it is structural. The Tolkāppiyam, the oldest extant Tamil grammar, opens its Poruḷatikāram — the book on subject-matter — by declaring that the foundation of all akam poetry is two things: நிலம் and பொழுது, land and time. The sūtra (Akattiṇai-iyal 4) reads: muthal eṉappaṭuvatu nilam poḻutu iraṇṭiṉ iyalpu eṉa moḻipa iyalpu uṇarntōrē — what is called foundational is, those who understand it say, the nature of these two: land and time.
This is not landscape as backdrop. The five tiṇais — kuṟiñci (mountain), mullai (forest), marutam (riverine farmland), neytal (coast), pālai (desert) — are five lands, and the word tiṇai itself means both land and genre. Because in Tamil poetics they are the same thing. The mountain-land is the union-of-lovers genre. The forest-land is the patient-waiting genre. The desert-land is the separation genre. Every emotion has its நிலம், and every நிலம் has its emotions.
Sanskrit பூமி (pūmi, from bhūmi) arrived later and did not displace நிலம். It specialised. பூமி took the cosmic register: Mother Earth (பூமி தாய்), the planet, the element. நிலம் kept the immediate ground. The two words now divide what was once one word’s territory.
The modern shift is the sharper one. நிலம் has narrowed toward property. நிலம் வாங்குதல், நிலம் விற்றல், நில அளவை, நில உரிமை — the most common environments of the word today are administrative and transactional. The Sangam sense, where நிலம் was the foundational category of emotional life, survives now only in literary scholarship. The word that once organised what could be felt now mostly organises who owns what. The ground stayed; the meaning above it kept moving.
Etymology phylogeny
Time runs left to right. Solid lines mark descent; dashed lines mark semantic borrowing.