太郎 is a masculine given name documented in Japanese. English Wiktionary traces it to Middle Chinese. English Wikipedia gives the meaning “eldest son”.
Late Middle Chinese origin
Source-reported
Meaning: “eldest son”
Appears to be a coinage within Japanese from Middle Chinese-derived elements, as a compound of 太 (ta, “fat; great”) + 郎 (rō, “boy”). Initially used as a given name for an eldest son. Attested since at least the early 900s.
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