Origin

The character 錬 combines the metal radical 金 on the left with 東 on the right. The metal radical tells you this kanji relates to metalworking, while 東 is mainly a sound hint that suggests the pronunciation レン. The character emerged from the idea of working metal through repeated heating and hammering — the core sense of tempering — and the repeated physical action extends naturally to other meanings like drilling, training, and polishing through practice. Over time, the meaning broadened from the metalworking process itself to any kind of repeated refinement or discipline.