(n.) a highly venomous snake, often with a characteristic hood
Cobra is a Portuguese word, and essentially means ‘snake with the hood’.
Despite having a Portuguese name, cobra snakes aren’t native Portugal, of course. Instead, that name probably entered the language via Portugal’s colonies in central Asia—most notably Goa, Calicut, and the other Indian seaports that proved massively important trade centres in the Portuguese Empire.
The word cobra itself—the Portuguese word for ‘serpent’—has its roots in Latin, and comes from colubra, a Latin word for a female snake. (No one is entirely sure where that Latin word has its roots, but a not-too-outlandish theory suggests it might be related to colus, the Latin word for a spinner’s distaff.)
That word, cobra, was used in Portugal’s Indian territories at expense of the snakes’ local Indian name, nāga. Derived from the Sanskrit word for a serpent, it remains in use in Hindu and Jainist mythology to refer to a legendary race of half-human, half-snake beings. (And it’s also, presumably, the inspiration for the name Nagini in JK Rowling’s Harry Potter stories.)