Translation from Chinese social media:
"Inspired by
@abcboy101 the Chinese dataminers looked into items in the alphabetical order lists in different languages.One specific new item (#2549) caught their eyes, it's between "Tera shard Ground" and "Tera shard electric" in Japanese"
Twitter image
"If it wasn't obvious enough, this is a new Tera shard, as all Tera shards are called "Tera shard (type name)" in Japanese. Very likely for you to change your Pokemon into the new Tera type.
Now, what could it be if it's between Ground and electric in Japanese?"
"Ground (じめん) starts with じ, while electric (でんき) starts with で.For starters, the Japanese alphabet goesさ"し"すせそ-たちつ"て"と so whatever the type name is must be between these two letters.Current suggested name from leakers is すてら/ (Stella/Stellar)"
Another Twitter image
"In Chinese, we call tera shards "(Type name) Tera shards". So the type name comes first in Chinese.They concluded it should start as "Xin" or "Xing" in Chinese, which also fits the previous hint from leakers "Xingjing", translates to "Star-crystal"."
"In the numerous characters combination that fits this hint, if we write it into "星晶" then it will mean "Star-Crystal" or "Star shaped Crystal".
Don't you think it looks just like what's in this image?
What do you think it will be called in English?"
Yet another Twitter image