noun
Refers to a record of descent, a family tree, or the line of ancestry. Also used figuratively for the historical development or lineage of ideas, schools, or traditions.
彼は自分の系譜を調べて、先祖が武士だったことを知った。
He researched his genealogy and learned that his ancestors were samurai.
この思
This thought traces its lineage back to ancient Greek philosophy.
系 (lineage, system) + 譜 (record, chart). The combination naturally yields 'genealogical record' or 'lineage chart'. The exact historical derivation is uncertain, but the kanji components transparently reflect the meaning.