noun
Refers to the state of not trusting someone or something, or the act of discrediting. Often used in formal or written contexts.
彼の不信用な態度が問題になった。
His distrustful attitude became a problem.
その噂は会社の不信用を招いた。
The rumor brought discredit to the company.
Compound of 不 (negative prefix) and 信用 (trust, credit). The exact historical derivation is uncertain, but it follows a common pattern of forming abstract nouns with 不.