poilu (n.)youdaoicibaDictYouDict[poilu 词源字典]
French private soldier, 1914, from French poilu, literally "hairy," from poil "hair," not of the head, but of beards, animal coats, etc., from Latin pilus (see pile (n.3)). In 19c. French the adjective had a secondary sense of "strong, brave, courageous" (Balzac).[poilu etymology, poilu origin, 英语词源]
private (n.)youdaoicibaDictYouDict
1590s, "private citizen," short for private person "individual not involved in government" (early 15c.), or from Latin privatus "man in private life," noun use of the adjective; 1781 in the military sense, short for Private soldier "one below the rank of a non-commissioned officer" (1570s), from private (adj.).