Is field named "language" somehow special? - elasticsearch

Question

In my query I have following filter:
"term": {
"language": "en-us"
}
And it's not returning any results despite there are a lot of docs with "language" = "en-us" and this field is defined in the mapping correctly. When I change filter for example for:
"term": {
"isPublic": true
}
Then it correctly filter by "isPublic" field.
My suspicion here is that field named "language" is treated somehow special? Maybe it's reserved keyword in ES query? Can't find it in docs.
ES v2.4.0
Mapping of document:
"mappings": {
"contributor": {
"_timestamp": {},
"properties": {
"createdAt": {
"type": "date",
"format": "epoch_millis||dateOptionalTime"
},
"displayName": {
"type": "string"
},
"followersCount_en_us": {
"type": "long"
},
"followersCount_zh_cn": {
"type": "long"
},
"id": {
"type": "long"
},
"isPublic": {
"type": "boolean"
},
"language": {
"type": "string"
},
"photoUrl": {
"type": "string",
"index": "not_analyzed"
},
"role": {
"type": "string",
"store": true
},
"slug": {
"type": "string",
"index": "not_analyzed"
}
}
}
}
}

Answer 1

The field language is nothing special. It should be all in the mapping. Several possible causes come to mind:
query analyzer != index analyzer
the analyzer first splits into two tokens, en and de and then throws away short tokens, which would leave both, query and index empty:-)
the field is not indexed, just stored.
The - is not a normal ascii dash in the index or the query. I have seen crazy things happening when people paste queries from a word processor, like quotes are no longer straight quotes, dashes are ndash or mdash, ü ist not one character but a combined character.
EDIT after mapping was added to the question:
The type string is analyzed with the Standard Analyzer which splits text into tokens in particular at dashes too, so the field contains two tokens, "en" and "us". Your search is a term query, which should probably be called token-query, because it queries exactly this, the token as you write it: "en-us". But this token does not exist in the field.
Two ways to remedy this:
set the field to not-analyzed and keep the query as is
change the query to a match query.
I would rather use (1), since the language field content is something like an ID and should not be analyzed.
More about the topic: "Why doesn’t the term query match my document?" on https://www.elastic.co/guide/en/elasticsearch/reference/2.4/query-dsl-term-query.html