Sei'ar beIsha Erva = A Woman's Hair is Erva. What Hair?

On Berachot 24a, Rav Sheshet states that "hair by a woman is erva." The context, which Rashi explains applies as well here, is in terms of whether one can say keriat Shema in front of a woman's exposed head of hair.

There are some difficulties in this. After all, non-married women go about with uncovered head, and indeed that is a way of knowing that a betula as opposed to an almana is getting married. If it is really erva, how could they go about in this way. Furthermore, on Ketubot daf 72, there is a derasha from Tanna deBei Rabbi Yishmael from a sota, that since the kohen uncovers her head, from here a warning to Jewish women not to go about with uncovered (/unbound hair). What need for this -- if it is erva, of course one cannot go around with erva exposed!

We can interpret it in that it is erva in terms of causing sexual excitement. So translates Soncino, in fact. Therefore, facing it while saying keriat Shema is distracting. In terms of practical halacha, many poskim make the distinction that it is only an erva in cases when it is usually covered. Thus, an unmarried woman or a gentile woman's uncovered hair, where they normally leave it uncovered, presents no problem in terms of reading Shema. But this is an involved sugya, which I am not going into here. I just wished to present this by way of background.

Now, on to the proposed chiddush.

I would propose that "Sei'ar beIsha Erva" actually refers to a woman's pubic hair, rather than to her head of hair. For that seems to be the context on the daf, and it resolves the aforementioned difficulties.

Earlier on the daf, on Berachot 24a, we have:

ותניא אחריתי הישן במטה ובניו ובני ביתו בצדו הרי זה לא יקרא ק"ש אא"כ היתה טלית מפסקת ביניהן ואם היו בניו ובני ביתו קטנים מותר

...

אמר מר אם היו בניו ובני ביתו קטנים מותר ועד כמה אמר רב חסדא תינוקת בת שלש שנים ויום אחד ותינוק בן ט' שנים ויום אחד איכא דאמרי תינוקת בת י"א שנה ויום אחד ותינוק בן שתים עשרה שנה ויום אחד אידי ואידי עד כדי (יחזקאל טז) שדים נכונו ושערך צמח

And it was taught in another [place]: If a man is in bed and his children and the members of his household are at his side, he must not recite the Shema' unless there is a garment separating them, but if his children and the members of his household are minors, he may.

...

The Master said: 'If his children and the members of his household were minors, it is permitted'. Up to what age? — R. Hisda said: A girl up to three years and one day, a boy up to nine years and one day. Some there are who say: A girl up to eleven years and a day, and a boy up to twelve years and a day; with both of them [it is] up to the time when "Thy breasts were fashioned and thy hair was grown." {Yechezkel 16:7}

The hair in this case is hair indicating maturity, and thus refers to pubic hair.

ז רְבָבָה, כְּצֶמַח הַשָּׂדֶה נְתַתִּיךְ, וַתִּרְבִּי וַתִּגְדְּלִי, וַתָּבֹאִי בַּעֲדִי עֲדָיִים: שָׁדַיִם נָכֹנוּ וּשְׂעָרֵךְ צִמֵּחַ, וְאַתְּ עֵרֹם וְעֶרְיָה.

7 I cause thee to increase, even as the growth of the field. And thou didst increase and grow up, and thou camest to excellent beauty: thy breasts were fashioned, and thy hair was grown; yet thou wast naked and bare.

The gemara continues a bit later with a question:

א"ל רב מרי לרב פפא שער יוצא בבגדו מהו קרא עליה שער שער

R. Mari said to R. Papa: If a hair protrudes through a man's garment, what is the rule? — He exclaimed: 'Tis but a hair, a hair!

The question here is whether, if a hair protrudes through a man's garment, is this indecency? Obviously this is not referring to the hair on his head, but rather to pubic hair, which is why one could have a question whether it is indecent. The reply is that it is but a hair, a hair! That is, it is nothing. It is not erva.

The gemara, a bit later, has:

אמר רב ששת שער באשה ערוה שנא' (שיר השירים ד) שערך כעדר העזים

R. Shesheth said: A woman's hair is a sexual incitement, as it says, Thy hair is as a flock of goats.

Shir Hashirim 4:

א הִנָּךְ יָפָה רַעְיָתִי, הִנָּךְ יָפָה--עֵינַיִךְ יוֹנִים, מִבַּעַד לְצַמָּתֵךְ; שַׂעְרֵךְ כְּעֵדֶר הָעִזִּים, שֶׁגָּלְשׁוּ מֵהַר גִּלְעָד.

1 Behold, thou art fair, my love; behold, thou art fair; thine eyes are as doves behind thy veil; thy hair is as a flock of goats, that trail down from mount Gilead.

We could interpret this as in line with the previous statement. It is true that for a man, a protruding pubic hair is not considered indecency (in whatever context it would or would not be). However, a woman's public hair protruding out of her clothing would be considered erva, perhaps because of sexual excitement it would cause.

The problem is that the prooftext certainly seems to be talking about the hair on the woman's head, and furthermore the proximity to and pattern after qol beIsha erva. But perhaps this can be resolved as, e.g., explaining that since woman's hair in general has this attractiveness, in this particular instance we would consider this type of hair to be erva by a woman, even though we do not for a man.

But such a reading would explain why unmarried women may go around with rosha parua and why a special derivation is required there.