The notion of a cryptographic key was created by analogy to physical locks and keys, but it looks like the cryptographers may have had the deeper insight: the authorizing function of any "key" (a PGP key, a door key, a voting machine key) is really a relatively tiny amount of information (usually digital information, even in the case of pin-and-tumbler locks, since there are typically explicit digital descriptions of any key: note that "[a]ll lock makers assign [integer] values to each pin depth so that keys can be replicated by number rather than requiring the physical key", per Marc Tobias's explanation of bump keys, which includes a nice diagram of the fact that door keys are really physical analog approximations of what their manufacturers conceive of as small digital secrets).
The neat new example of this: a photograph of a pin-and-tumbler lock key is equivalent to the key itself. Not only can you make photographs from keys, you can make keys from photographs.
My roommate pointed out that the ubiquitous farewell "ciao" (known to Brazilians, for instance, as "tchau") actually means "slave".
Wikipedia agrees that the word comes from an abbreviation of a phrase akin to Italian "sono vostro schiavo" ("I am your slave"). This sounds less bizarre in the context of ancient letter closings like "I beg to remain / your most humble and obedient servant", but it's still pretty weird to modern ears.
"Schiavo" is still the modern Italian term for "slave" (that's what Terri Schiavo's last name means, as far as I can tell); compare Portuguese "escravo" and Spanish "esclavo". (I think that the name of the city and river Escravos in Nigeria is a reference to the Portuguese Atlantic slave trade. Nigeria lay along what was formerly known as the "Slave Coast", akin to the Gold Coast and Ivory Coast. The Slave Coast is no longer so called, yet Nigeria still has a city whose name means Slaves.)
The other bizarre thing is that, if we believe Wikipedia, all of these words -- "Escravos" as well as "ciao" as well as the English word "slave" -- actually derive from the name of the Slavs because of their propensity to be enslaved as prisoners of war in classical antiquity.
