The ware "Thatch Reed" is used for other things than thatching, although that's its primary function for the Barbarians. I think the term is especially confusing for the Frisians, because it's not only used for sails but for fishing nets as well.
So, I am thinking of doing the following changes:
- Rename the ware "Thatch Reed" to "Reed"
- Rename the immovable "Reed" to "Reed Field"