Correct spelling for the English word "coost" is [kˈuːst], [kˈuːst], [k_ˈuː_s_t] (IPA phonetic alphabet).
The word "coost" does not have a widely known or recognized etymology. It appears to be a regional or dialectal variation of the word "cast" or "cost", which means to throw or to propel with force. "Coost" is commonly used in Scottish Scots, particularly in the Glasgow area, where it is an alternative spelling or pronunciation of "cast". However, it is important to note that the term "coost" may have different origins in other dialects or languages, so its precise etymology may vary in different contexts.