The Games section of the daily New York Times includes the Spelling Bee, a challenge to spell as many words as one can using only seven letters, one letter required to be used in every word. Along the way the player attains certain sophomoric goads to success - Beginner, Solid, Awesome, Genius and Queen Bee, the last for finding all of the approved words in the puzzle. I say approved words advisedly since some words, at least, are proscribed on proper grounds - such as racial slurs, obscenities, vulgarities and so on.
One might expect the rules to lead to fairly straightforward results: no personal or place names, nor words derived from names are used unless they otherwise have an ordinary referent ("Albanian" or "Germanic" for example aren't allowed, but "neapolitan" or napolean" are fine because they refer to things, in this case desserts). This is a tacit rule. One might also expect that the range of permissible words might (tacitly) be limited to English, at least in its American version, but this isn't the case.
In fact there seems to be a bias against perfectly good English words that either the wordbot doesn't know, or that the editors don't; or those that they decide are too obscure or arcane for the average English speaker (both arcane and arcana are permitted). So words like trinitarian, antinomian, antinomy (see Kant's Critique of Pure Reason), marmoreal or porphyry are not, for the puzzle setters, words at all. Antinomy can't pass muster but antimony does. On the other hand lots of words creep into the language from all directions. Lanai (a Hawaiian verandah) is ok (and so is verandah, an Anglo-Indian word like bungalow); but liana (a tropical vine) isn't; raita (a yogurt dressing in Indian cuisine) is good, but riata (a woven rope used by Argentine gauchos) is verboten, as is verboten verboten.
What's more, English also contains a fund of French words in common usage, but which ones count is also arbitrary - entente and detente, bonbon and restaurant are fine, but pensee isn't, nor auberge, aubergine, courgette. Italian musical terms are permitted - lento (but not lenten, as in the season between Good Friday and Easter), tutti, allegretto, molto, etc. Nor is most British English except where it opens the prospect of alternate spellings (catalog/catalogue, dialog/dialogue, ton/tonne). Twit is fine but not twat; and why not wank/wanker or bollocks?
You learn the rules by trying things out - the black box approach. All of this experimentation, however, cannot prepare anyone for the completely whimsical admission of obscure foreign words. You may get by with sirocco (a seasonal wind blowing northward from the Sahara across Spain), but not with lebeche nor cierzo (also seasonal Spanish winds); no mistral (a French wind); but haboob, a trans-Saharan wind is just fine. So is haka (a Maori ritual celebration); lantana (a tropical verbena); llano (a Spanish prairie) but not llanta (a Spanish tire). And there is a catalog of permissible Latinate words (though not "Latinate" itself): I give you but one exhibit A - torus, and its plural forms, tori and torii (a surface of revolution generated by a revolving circle in three-dimensional space one full revolution about an axis that is coplanar with the circle - think 'donut').
It's enough to make a person cynical. What was wrong with porphyry, then? And there are those words, presumably English ones, which no one would ever use - openable comes to mind, or nonillion (nine millions), catalytically, deckle (a peculiarly Canadian version of decal). It is just this organic mushiness of a language that keeps it alive and evolving but drives a puzzler to desperate measures: finally at the end of a daily puzzle with maybe three words remaining to find, one's baser instincts come into play and a kind of corrupt invention takes over. One begins to concoct a kind of mad syllabic stew, a jaundiced eye for easy composites: turdhammer (Harbor Freight, only $14.99); slackwad (available on Amazon in plumbing supplies); brassball, globel, globulment . . . but here I go. It is the debasement of the imagination, the beginnings of a new strain of dementia.