From the verb 疲る (tsukaru), itself derived from 尽く (tsuku), meaning "to be used up" or "to run out." The する/れる suffix marks it as a spontaneous intransitive state — tiredness that *happens to* the subject rather than something they do deliberately. The kanji 疲 (hi) combines the "illness" radical 疒 with 皮 (skin), evoking a body worn down to the skin.

In Japanese work culture, expressing that one is 疲れた (tsukareta) is very common and socially acceptable. The set phrase お疲れ様です (otsukaresama desu) — literally "you must be tired" — is a ubiquitous workplace greeting used when a colleague finishes a task or leaves for the day. It signals respect and solidarity, not just acknowledgment of fatigue. Using this phrase correctly will make you sound naturally fluent in professional settings.