There were many soto maker who call him foot soto mister "X" or with another names at that time. The term itself started to spread and used as the general term for the same dish by another soto maker when mister X closes his shop in 1991.
Soto is sometimes considered Indonesia's national dish, as it is served from Sumatra to Papua, in a wide range of variations. Soto is omnipresent in Indonesia, available in many warungs and open-air eateries on many street corners, to fine dining restaurants and luxurious hotels. Soto, especially soto ayam (chicken soto), is an Indonesian equivalent of chicken soup. Because it is always served warm with a tender texture, it is considered an Indonesian comfort food.
Because of the proximity and significant numbers of Indonesian migrants working and settling in neighbouring countries, soto can also be found in Singapore and Malaysia, and has become a part of their cuisine.
Introduced to Suriname by Javanese migrants, it is part of the national cuisine of that country as well, where it is spelled saoto.
Nowadays, we can find this dish almost everywhere in Jakarta.Sources :
https://en.wikipedia.org/wiki/Soto_(food)
https://id.wikibooks.org/wiki/Resep:Soto_Betawi