Using the word “dream” as hope for the future across languages

Question

Many languages seem to use the same word for "dream" (psychological phenomenon) and "dream" (hope for the future). Quick scanning on Wiktionary gives the list:

• Germanic languages: Danish (drøm), Dutch (droom), English (dream), German (Traum), Luxembourgish (Dram), Norwegian (drøm), Swedish (dröm), West Frisian (dream)
• Romance languages: Catalan (somni), French (rêve / songe), Galician (soño), Italian (sogno), Portuguese (sonho), Romanian (vis), Spanish (sueño)
• Slavic langauges: Czech (sen), Latvian (sapnis), Slovak (sen)
• Greek (όνειρο)
• Hebrew (חלום)
• Indonesian (mimpi / impian)
• Japanaese (夢)
• Korean (꿈)
• Marathi (स्वप्न)
• Tagalog (panaginip)
• Turkish (düş)

In some languages, the words for the latter meaning of "dream" seem to have been derived from the words for the former:

• Chinese (夢想 from 夢)
• Finnish (unelma from uni)
• Thai (คาดฝัน kʰâːt fǎn or คิดฝัน kʰít fǎn, from ฝัน făn)

Some languages use different terms:

• Georgian (სიზმარი sizmari vs. ოცნება otsneba)
• Lithuanian (sapnas vs. svajonė)
• Malay (mimpi vs. impian)
• Polish (sen vs. marzenie - however, it is possible to call the psychological phenomenon marzenie senne, which is a more technical term than sen)
• Russian (сон son or дрёма ˈdrʲoma vs. мечта mɛtʃˈt̪a)
• Telugu (కల kala vs. స్వప్నం svapnaM)
• Ukrainian (сон son vs. мрія mríja)
• Yiddish (חלום kholem vs. טרוים troym)

My questions are following:

1. Have such usages of the word "dream" been developed independently, or are they mere calques from a single language?
2. If they have been developed independently, is there any linguistic speculation about how the two meanings of "dream" relate?

Answer 1

This phenomenon is a specific case of how each language uniquely divides up the semantic space.

The real world of referents is not divided up neatly into semantic categories that we can directly turn into lexical categories. A classic example is the color space. In the real world, there are an infinite number of colors in the spectrum, and the human visual system can distinguish between 100,000 to 10,000,000 of them. Of course, no language has 10,000,000 color words - instead, each language divides the spectrum up into ranges and has color names corresponding to those ranges. We know that different languages divide up the color space differently, e.g. the range yellow vs. green vs. blue is notoriously different from language to language. See for example the color divisions of Piraha [PDF].

This is not limited to colors. Fingers and toes, states and locations of existence, kinship terms, literally every concept is slightly differently divided and named. This division extends down to the idiolect, in fact.

What is happening is simply that each language has a unique mapping of abstract semantic fields to concrete lexical fields.

In this particular instance, you are seeing that some languages (like Polish) happen to use two separate lexical fields for "vision while sleeping" (sen) and "aspiration for the future" (marzenie), and some (like English) happen to use one lexical field for both (dream). I say "happen to" because largely this is the end result of a complex combination of linguistic and cultural evolutionary happenstance.

Russian uses two different words голубой goluboj and синий sinij for colors around 475 nm, while English uses one word blue. Similarly, Russian uses two different words сон son 'vision while sleeping' and мечта mjechta 'aspiration or reverie' for related concepts corresponding to the English lexical field of dream. The semantic field of "visions, aspirations, and reveries" is divided up uniquely.