I need some clarification. For me this question comes from pages 93-95 of the ΛΟΓΟΣ text. But it is a general question about noun genders.
What is the difference in usage between ἡ αὐλή and το αὔλιον? I understand that the former means “courtyard” while the latter means “sheepfold.” I am unclear as to why the change in meaning with the change in gender.
The Cambridge Greek Grammar (CGG) says αὔλιον is the diminutive of αὐλή. So αὐλή is an enclosure, couryard, farmyard etc while αὔλιον is a small enclosure like a livestock pen.
Nouns in -ιον (all neuter) are properly diminutives but often acquire a distinct meaning too. E.g. λόγος word, speech, λόγιον an oracle. But θηρίον is functionally scarcely different from θήρ a wild animal, while a δελτίον is just a small δέλτος (fem.) a writing-tablet.
P.S. Significantly, courtesans and slave-maids tend to have neuter diminutive names, e.g. Φιλημάτιον (“Kissy”), Γλυκέριον (“Sweetie”).
Thank you both. That clears it up!
Great range of examples Michael, thank you. I’ve added your comments as a footnote in my copy of CGCG 
Why is Sokrates called Σωκρατίδιον at least in Aristophanes’ Clouds? Is it affectionate?
It’s almost as if Socrates is a child, isn’t it—certainly not how anyone in Plato would address him! I suppose the tone is mock-affectionate, wheedling perhaps. Earlier in the play Strrepsiades calls to his son in similar fashion: Φειδιππίδη Φειδιππίδιον (80). The context is more revealing there—definitely wheedling, cajoling (until he turns to threats).
With women (never high-class, rarely respectable) it’s clearly a matter of objectification. The tone can be either affectionate (by lovers) or derogatory (by moralists). There’s also γύναιον, similarly two-edged.
Ἑρμῄδιον shows up a couple of times in Aristophanes’ Peace. The first time seems a normal sort of wheedling address:
382 Τρ. μή νυν λακήσῃς, λίσσομαί σ’, Ὦρμῄδιον.
But the second is just a bit odd:
923 Τρ. τί δ’ ἄλλο γ’ ἢ ταύτην χύτραις ἱδρυτέον;
924 Χο. χύτραισιν, ὥσπερ μεμφόμενον Ἑρμῄδιον;
A scholion explains it as Ἑρμίδιον: ἀντὶ τοῦ “εὐτελές”
Ἑρμίδιον and Ἑρμήδιον may have just been variant readings, and I imagine εὐτελές simply glosses μεμφόμενον.
The reference to the χύτραι will be to the last day of the Anthesteria, when an offering of pease pudding (cheap, chthonic) was made to Hermes.
Yes, there’s nothing odd about the ι for ῃ, which was pronounced the same by the later Greeks. Presumably the scholiast was commenting on a manuscript that used that spelling. Or alternatively, the scholion was modified when it was copied. I’ll note that Lucian uses Ἑρμάδιον in his Charon and Hermes dialogue, though that’s not really any more interesting.
As you say, the scholiast may have meant to write “μεμφόμενον ἀντὶ τοῦ “εὐτελές” and simply made a mistake and glossed the wrong thing.
I think that it’s likely though that the scholiast meant what he wrote, and thought that Aristophanes might call a person small or paltry by applying the diminutive.
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Entirely separate from the scholiast’s theory, however, is that there is a pattern of calling “little statues” of the Gods by the diminutive for that God’s name, which could also be related to what Aristophanes meant by it. See Ἀπολλωνίσκος, ἱερακίδιον, ἱππάριον, ἱππίσκος etc.