In reference to a person, the sense of "solidly built, strong and hardy" is from late 14c. Related: Sturdily; sturdiness. Sturdy-boots "obstinate person" is from 1762; a sturdy beggar in old language was one capable of work (c. 1400).
hi there! Yes, the Pellon interfacing specified is ultra thick and sturdy and creates the structure of the basket. You can find it by name at stores like Joanns Fabrics, Hobby Lobby and some Walmarts with a fabric section.