What is the Japanese word for Jello?

Answer 1

Jero or jeri

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This is not correct. It is actually ゼリー (zerii).

As is sometimes the case in the Japanese language, they've taken a foreign word which they turned into katakana, and made it their own. So taking that original foreign word and converting it straight into katakana makes a meaningless word.

Another example would be bread (パン, 'pahn') which an average japanese person wouldn't understand if you simply said or wrote 'bureddo' (ブレッド). Or 'cigarette' which they might understand if you said 'shigaretto', but the actual word they've adopted into use is 'tabako'.