信任
しんにん · shinnin · JLPT N1 · noun
trust; confidence; credence
信 — person 亻 + speech 言
信 combines 亻(person) with 言(speech), depicting a person standing by their words. The original sense is 'truthfulness' or 'sincerity'—what a person says can be trusted. From this it extended to 'believe,' 'trust,' and later 'message' or 'letter,' since a letter carries one's word.
任 — person radical 亻 + 壬 (phonetic)
任 combines the person radical 亻 with 壬, which supplies the sound. The original sense centered on a person bearing a load or burden, which extended naturally to 'carrying responsibility,' 'duty,' and 'to appoint someone to a post.' Modern uses like 任务 (task) and 责任 (responsibility) preserve this core idea.