How Religion: Islam became wrong Arabic word ( Muslim ) in here?

Is it all over in Openstreetmap?
for example:

religion — muslim

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That doesn’t explain the historic reason for this tag.

No, but it does answer the second question (“Is it all over in Openstreetmap”): Yes, this is an established tag and widely used.

Why this value was chosen is probably a lot harder to answer. It’s been around since at least 2008.

I wanted to point out the religion=muslim is a long existing tag (WikiPage was created in 2008).

OSM tags are just useful mnemonics, ideally using a word or phrase which people, especially non-English speakers, are likely to recognise. Furthermore they need to be usable by people who may not be familiar with precise distinctions. Muslim is widely used across many countries and languages. Other religions and denominations have tags which don’t reflect official names, e.g., quaker for “Religious Society of Friends” and mormon for the Church of Latter Day Saints. In all these cases the tag does the job of being recognisable & unambiguous.

Note that the tag religion=muslim is applied to various other things (schools, bookshops, …) other than amenity=place_of_worship, where I think islam would be wrong (they would be described as islamic).

As others have said the tag has been in existence for a long time (17-18 years) and changing a standard is very hard work, and I see little gain.

I assumed the adjective or believer form was chosen for religion=, like others (except for =shinto among the most common ones). Only that the reason is not clear.