Hopsack sounds like a contagious disease (cue my partner obsessing about The Walking Dead), but it's actually a type of fabric. It's a loosely woven wool material, similar to flannel or donegal, and is the perfect lightweight fabric for these early autumnal days.
Love that word... autumnal. It brings up warm memories like apple orchards, cider and cinnamon rolls. All that cozy, nostalgic stuff.
Anyway, it's a breathable wool and I'm probably going to live in them for the next month or two. I'll wear them with sneakers or a blazer for work. Wool wool wool every autumnal day!