The affix ḍhañ comes after the words kośa etc. in the sense of 'adapted to that'.,
This debars अण् ॥ Thus कोशे संभूतं = कौशेयं वस्त्रम् 'silken clothes'.
The word कोश means 'cocoon.' कौशेयः may literally therefore mean 'anything suited to the cocoon,' and may apply to the caterpillar as well as to the silk made out of cocoon. The word कौशेय is however रूढि and means 'silken.' Nor does it mean 'suited to the sheath,' as a sword, though kosa means 'sheath' also. This sutra would have been more properly placed after 4.3.134, under the heading of विकार rather than of संभूत ॥
In fact after the sutra एण्या-ढञ् 4.3.159, the addition of कोशाच्च would have been more appropriate.,