i always thought it was some sort of version of cravate

Cravat, meaning tie, comes from the French adjective for Croatian.

Cravenette, according to this website:

http://www.rtwear.com/glossary/c.htm

is a registered TM of the eponymous company. And according to this:

http://www.sdc.org.uk/pdf_features/JA99F2.PDF

they used to be a British company.