The affix aṇ comes the sense is 'a collection thereof' after the words bhikṣā etc.,
The repetition of the word अण् in this sutra, though its anuvritti was here, is for the sake of removing the operation of any obstructing rule.
Thus भिक्षाणां समूहः = भैक्षम् 'what is collected in the shape of alms'. So also गर्भिणी + अण् = गर्भिण् + अण् (the masculine form of a Bha is substituted, when a Taddhita affix follows without an indicatory ढ, भस्याढे तद्धिते) = गर्भिणः 6.4.164, In the case of युवति, the word however is not changed to its masculine form. Thus युवतीनां समूहः = यौवतम् 'a collection of young women'.
1 भिक्षा, 2 गर्भिणी, 3 क्षेत्र, 4 करीष, 5 अङ्गार, 6 चर्मन् (चर्मिन् according to some texts) 7 सहस्र, 8 युवति, 9 पदाति, 10 पद्धति, 11 अथर्वन, (also अर्वन् K.) 12 दक्षिणा, 13 भूत, 14 विषय, 15 श्रोत्र. also 16 धर्मिन्,