Nili,an acronym for the passuk from Shmuel, “Netzach Yisreal lo yishaker,” was originally the name (and password) of a spy organization that operated in Israel during WWI. It was led by members of the Aaronson family,who immigrated to Palestine from Romania, including Aron, his sister Sarah, some other Aronson siblings (not sure) and Avshalom Feinberg. Interestingly they were helping the British (who were our enemies when the Irgun & Lechi fought against them during British occupation later in the 20th century) under General Allenby fight against the Turks. I don’t know which one of them chose the name Nili, as above, for their group. The story is a very sad one, and they all died under tragic circumstances. Aron is the only one that was not definitely murdered by enemies. He died in a plane crash over the English Channel that may have been orchestrated by the British. (I know, the British were supposed to be his friends, but it’s a long sad story.) The Aronson home in Zichron Yakov has been preserved as a museum, and is an interesting place to visit. (Yes, I was there. Very interesting, but more sad than enjoyable.)
How the name of the spy organization became a popular Hebrew girl’s name, I don’t know.