Part of the ‘Antique Fabrics‘ series, this fabric isn’t necessarily extinct, but it was more popular in the past than the present.
Lightweight, loosely woven plain-weave cotton or worsted wool fabric. Étamine is similar to cotton gauze and cheesecloth. Historically derived from a fabric used to sift flour, hence the name (the French word for sieve).
Contemporary etamine is a finer, more tightly-woven fabric, somewhat akin to muslin. If looking for a good-enough match, along with gauze and muslin, consider challis or voile.