Is it a coincidence that "ethane" is "methane" with the m removed?

Genuinely a coincidence, and a good one, because the two words come from completely unrelated places.

Meth- traces back through "methyl" to a compound obtained by heating wood, and the name was built from Greek roots meaning roughly wine and wood — wood spirit, what we now call methanol.

Eth- comes from "ether", the volatile liquid, itself from a Greek word for the upper air. The two-carbon fragment got named after the substance chemists were already working with, and "ethyl" was coined for it.

So one name comes from wood and one from air, they were coined decades apart by different people for different reasons, and the fact that removing one letter turns one into the other is pure accident of transliteration.

The giveaway is exactly what you noticed: the pattern stops immediately. Propane comes from a fatty acid name, butane from butter. Only from pentane onwards does the system become systematic, using Greek number roots — pent, hex, hept, oct. The first four names are historical debris that the system inherited and never cleaned up.

The near-collision is even better than it looks, because it very nearly caused a real problem.

Spoken aloud in a noisy lab, "methyl" and "ethyl" differ by one consonant at the start of the word, and they name fragments that appear constantly, often in the same molecule. Anyone who has dictated a structure over a phone has had to say something like "methyl, M for Mary".

And "ethane" versus "ethene" versus "ethyne" is a second collision layered on the first — three different molecules distinguished by one vowel in the middle. Modern naming is precise and completely unsuited to being spoken, which is why chemists draw.

Worth adding just how much of chemical naming is this kind of debris, because it reframes the whole subject for people learning it.

The systematic scheme is genuinely systematic once you are past the first few members, and it can name any structure unambiguously. But it was imposed on a field that had already been naming things for a century, and the most common substances were the ones named earliest and therefore the least systematically.

That produces exactly the frustrating pattern students meet: the compounds you encounter first have arbitrary names, and the rules you are being taught only start working on compounds you rarely see. The system looks unreliable when in fact you are being shown its exceptions first, in order of how common they are.

One more coincidence in the same family, since we are collecting them: the prefix "pro" in propane has nothing to do with the Greek "pro". It is a truncation of propionic acid, whose name means "first fat" — it was the shortest acid still showing fat-like behaviour.

So the first three alkanes are named after wood, air and fat respectively. It reads like a joke and it is simply what happened.