The spelling of the word "yacks" may seem unusual, but it can be easily explained through IPA phonetic transcription. The word is pronounced as /jæks/ in IPA, with the initial "y" sound represented by the symbol for the consonant "j". The vowel sound is a short "a" pronounced as /æ/, with a final "ks" sound represented by the symbol for the consonant cluster "ks". Despite its unconventional spelling, "yacks" is a valid word used to describe the sound of loud, harsh laughter.
The word "yacks" does not have a specific etymology, as it is considered to be a slang term. Slang words often emerge from various sources, but their precise origins can be challenging to trace. In the case of "yacks", it is possible that it could be a derivative of the verb "yak" which means to talk incessantly or to chatter. However, without further historical evidence or documentation, the exact etymology of "yacks" cannot be determined definitively.