anantāsana
pose of Ananta, pose of the endless one
ananta/‘that which has no end’
a(n) + anta/not + end
The following note is about nothing but language.
Just as in Greek, Sanskrit’s negative prefix a- appears instead as an- when followed by a vowel, as seen in these words from Greek:
atom a-tomos/no-cut (indivisible)
apathetic a-patheia/no-suffering, no-affect
but
analgesic an-algēsia/no-pain
anomalous an-omalos/not even, not same
ananta/no-end, endless, without end belongs a type of formation widespread across the Indo-European languages, including English.
The Sanskrit grammarians labelled it with an example, bahu-vrīhi/‘much-rice’ = rich, wealthy. They can be called possessive compounds in English, but ‘bahuvrihi’ also gets used in linguistic discussions.
English examples come in the thousands. They assign characteristics to people and things: redhead, bigwig, humpback, blue-fin, redcoat, three-tonne, five-inch, hatch-back, two-tone, blue-collar, heavy-weight, no-nonsense. Insults are prominent: dimwit, dickhead. (A list on wiktionary.)
Blackbird and Blackbeard look alike on the surface but only the second is a bahuvrihi. A blackbird is a bird, but Blackbeard is not a beard but a pirate—whose beard is black.
In English such words usually refer to settled characteristics (like features possessed by different types of car: four-door, rear-drive, hatch-back), and this seems to be the normal style across the Indo-European languages. They are particularly common in names: Socrates (‘safe power’), Siddhartha (‘achieved goal’), Lionheart, Whitehead. In the earliest stage of Sanskrit (‘Vedic Sanskrit’) that usual scheme applies, but in the later ‘classical Sanskrit’ (from mid-first millennium BCE) they take on a whole new role and importance: they get used not only for settled characteristics but for passing states of the moment. A bluestocking is a kind of person in English, but in classical Sanskrit a bluestocking could also be someone who just now happens to be wearing stockings that are blue.
Because they were so important a tool in the language and because confusions can arise (since there may be no explicit sign that the word is a bahuvrihi—Blackbeard looks like Blackbird—and context has often been packed away inside the word), the Sanskrit grammatical tradition devised a neat system for analysing bahuvrihis by turning them into relative clauses:
dimwit: someone whose wits are dim is a dimwit.
hatchback: a car whose rear door opens like a hatch is a hatchback.
two-term: someone (a president) who served two terms is a two-term (president)
Simply negated versions are possible in English (such as no-nonsense) but are awkward and so limited in number and use, but abound in Sanskrit and Greek:
an atom is literally something for which there is no cutting, and ananta is something that has no end.