how did ice get its name?

Scroll down below the definitions to see the word's origin:

http://www.answers.com/ice

It'll tell you this: [Middle English is, from Old English îs.]

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Also interesting reading here:

http://www.etymonline.com/index.php?search=ice&searchmode=none

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when did frozen water known as ice,get its name and orgin?

From that last link:

O.E. is "ice," from P.Gmc. *isa- (cf. O.N. iss, O.Fris. is, Du. ijs, Ger. Eis), with no certain cognates beyond Gmc. Slang meaning "diamonds" is attested from 1906. Ice cream is first recorded 1688 (as iced cream); icing in the sugary sense is from 1769; ice cube first recorded 1929. To break the ice "to make the first opening to any attempt" is from 1590, metaphoric of making passages for boats by breaking up river ice though in modern use usually with implications of "cold reserve."

If you look at the approximate dates for Old English and Middle English, you'll see why there is no way to give an exact time of origin.
Old English: http://en.wikipedia.org/wiki/Old_English_language
(Middle English: http://en.wikipedia.org/wiki/Middle_English )

Also, in bold above, it states that there are "no certain cognates beyond Gmc" -- which tells you that that's as far back as etymologists seem to be able to trace this word.

If I had to give a when and where, my best guess would be mid-5th century AD in West Germanic areas of England, Scotland, etc.
http://en.wikipedia.org/wiki/West_Germanic_language
http://en.wikipedia.org/wiki/English_language
(Scroll down to History)

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To understand how ice got its name, we need to look at the word's etymology. The English word "ice" can be traced back to the Old English word "is" or "īs," which later evolved into the Middle English word "ice." The word has Germanic origins and is related to similar words in other Germanic languages, such as the German "Eis" and the Dutch "ijs."

The origin of the word can be further traced back to the Proto-Germanic word "īs" and the Proto-Indo-European root "*h₁eyH-," meaning "frost" or "ice." This root is also the source of other related words like "icy" and "frost."

So, the word "ice" obtained its name based on how it has been referred to in the English language for hundreds of years, ultimately stemming from ancient Germanic and Indo-European origins.