Quiz: Remember the definition of mal de mer?
c.1200, "bold, daring, fearless," from Old French hardi, from past participle of hardir "to harden, be or make bold," from Frankish *hardjan, from Proto-Germanic *hardjan "to make hard" (cf. Old Frisian herda, Old High German herten, Old Norse herða, Gothic gahardjan "make hard;" see hard). Sense influenced by English hard. Related: Hardily; hardiness. Hardhede "physical hardiness" is attested from early 15c.