What was the Earlier name of 'HINDUS'​

According to Klaus Klostermaier, the term Vaidika dharma is the earliest self-designation of Hinduism. According to Arvind Sharma, the historical evidence suggests that "the Hindus were referring to their religion by the term vaidika dharma or a variant thereof" by the 4th-century CE

from the conditions of the working class in england by friedrich engels,the main idea is :

i'd assume india mainly because of how isolated japan was.   plus it is a whole china away.