Sorry, this seriously is an honest question: Is there a typo in your post? Otherwise I must come to the conclusion that you suggest pronouncing JS as 'jiss'.
JS would be hard to trademark now because there’s so many other services using JS as part of their trademark. There’s also already quite a few companies who’ve already registered JS as a trademark.
You also couldn’t call it Jscript because Microsoft owns the trademark there.
EMCAScript is the most practical from a legal standpoint, but that name sucks badly.