疲れてきた

The word '疲れてきた' is a compound expression. Let's break it down: 1. **疲れ (Tsukare):** This is the noun form of the verb '疲れる' (tsukareru), meaning 'to get tired' or 'to become fatigued.' Its origin can be traced back to classical Japanese, where '疲る' (tsukaru) or '倦る' (karu/tsukaru) had similar meanings of exhaustion or weariness. The kanji 疲 is a phono-semantic compound, with 疒 (disease radical) indicating something wrong with the body, and 皮 (skin/hide) representing something stretched or worn out, metaphorically suggesting the body being worn out. 2. **て (te):** This is a conjunctive particle, often used to connect verbs or to form a continuous aspect. In this case, it connects '疲れる' with 'くる'. 3. **きた (kita):** This is the past tense of the verb 'くる' (kuru), meaning 'to come.' When 'くる' is used in conjunction with the '-te' form of another verb, it often indicates a change that has been occurring over time and is now evident, or a process that has started and is continuing up to the present moment. It conveys a sense of something 'coming into being' or 'starting to happen.' Therefore, '疲れてきた' literally translates to something like 'tiredness has come' or 'has come to be tired.' More naturally, it expresses the onset and continuation of fatigue – the feeling of *starting* to get tired or becoming progressively tired. It implies a gradual process rather than an instantaneous state of being tired.