The Collaborative International Dictionary of English v.0.48:
Nainsook \Nain`sook"\, n. [Nainsukh, a valley in Kaghan.] A thick sort of jaconet muslin, plain or striped, formerly made in India. [1913 Webster]WordNet (r) 3.0 (2006):
nainsook n 1: a soft lightweight muslin used especially for babies