I was reading in Shevlei Haleket (13th century) that women rest from sunset to the counting of the omer. R. Simcha from Spiers says that this is because the students of Rabbi Akiva died toward sunset. The author (R. Zedkiayah the Physician from Roma) felt this was inadequate as it does not explain what women have to do with it. He suggests that like in Berashit Rabah and the Y. Sanhedrin that since women caused death, they proceed the men after the burial cot. Since they did this for the students of R. Akiva, women take off in honor of these rightgeous women. (Not everyone like the idea of the women being in front of the bus so to speak, so some communities put them in the back.)
The parallel with Channukah (women do not work when the candles are lit) and Rosh Chodesh (woman don't work) are obvious. I think that all three customs have a similar origin. Maybe the wanted to guarentee women two weeks paid vacation.