When God first created The Land and its first people, He taught them to speak. He also explained to them that there are many other worlds throughout the universe, and that some of those worlds are inhabited by sentient beings which He had also created. (Some sentient races, He said, were much like the people of the Land, and some were very different, but all were fundamentally equal in His eyes and His heart.) And each race developed its own language; on some worlds, sentient races might develop several different languages. These languages might even take entirely different forms, though the most common form was vocal, as was the case of the Land's language. God also told the people He had created on the Land that He had imbued them with a sense which had never before been granted to any other race, a sense which allowed them to tap into the collective unconscious of the Universe, so that whenever they heard an unfamiliar word from an alien world, with just a little thought the meaning of that word should become clear to them. The sense also allowed them to come up with alien words to describe things or ideas for which they had never heard a name. Such words came to be known as "subwords" (because of an inexplicable tendency Landians have to confuse the words "unconscious" and "subconscious"), and the sense instilled in the Landian race by God was therefore referred to as our "subword sense."
While most Landians have at least heard of the existence of other languages, it is a fact which is easy for them to forget, because we all speak the same language, unlike on some planets (such as Earth). In fact it isn't terribly uncommon to forget the word "language" even exists, because its use would imply the existence of more than one, a concept which the Landian mind tends to reject. One might think that the existence of the subword sense would serve to remind them that there are other languages, but in fact this sense is only rarely activated. The majority of concepts one might need to think about or express are already covered by the language God taught to the first people, and certain new things or ideas which require names may not even exist on other worlds, and is therefore up to Landians to bestow names upon. And on those occasions when the subword sense does kick in, people simply incorporate the new words into their extant vocabulary, and soon forget that these words originated from other languages.
It should be noted that if a word exists in the original Landian vocabulary, or is a word later made up by Landians, rather than being a word of alien origin, that word will not be covered by the subword sense, and will therefore need to be taught to people in the normal way, or looked up in a dictionary. It should further be noted that within most languages in the Universe there exist synonyms for certain concepts, and when one takes into account the fact that many different alien languages are likely to contain their own words for the same concepts, and it is therefore somewhat arbitrary which word within a single language or even from which world's language a subword will occur to Landians. However, it's not entirely arbitrary; in the first place, only vocal languages are covered by the subword sense, and those languages may themselves differ in form from species to species. Therefore, subwords will usually come from languages which are most compatible with Landian vocal chords, as well as sounding... not too extremely alien to Landian ears. Because Landian physiology and psychology are most closely related to that of Terrans (and perhaps also to an extent because of Landians' more intense inherent interest in Terran culture), it is Terran words which most commonly occur to Landians as subwords (though there certainly are subwords from other planets besides Earth that have entered the Landian vocabulary). Of course, even on Earth, there are many different languages, so again it may become somewhat arbitrary as to which Terran language is used. The mechanism by which a specific word or language is selected rather than synonyms which might just as well be used is not understood; God never explained whether it is entirely random or whether in fact there is some specific reason for it, though people have sometimes noticed that there seems to be some correlation between the reason or context in which they're trying to think of a word, and which word occurs to them. This, however, is not always the case, and so it is assumed that there most likely is some randomness to the selection, whenever a given situation seems to contain no real determining factors.
It should also be noted that the subword sense is seemingly stronger in some people than in others, and of course some people are more interested in the idea of subwords than are others. One such person was Perryh, who founded the Experimental Linguists' Club in LY 135. The ELC's members (called elcs) are people who devote a certain amount of time to trying to think of new subwords, forcing the sense to kick in instead of waiting for it to happen as the specific need arises. Because of this, their minds become more attuned to the sense, which makes it easier for it to kick in on its own, and more than just thinking of new words, when they hear or read subwords that have been introduced by others, the meaning becomes clear to them more quickly than it does for most people.