Why do cash registers say, “insert document to be franked”? Who’s Frank?

Dear Cecil: Living as I do within spitting distance of our nation’s capital, I know that congresspersons can mail pieces of allegedly official business in “franked” envelopes, which require no postage. I never thought about the terminology until I noticed that when you pay by check at some supermarkets, the electronic register tells the cashier to “Insert Document to be Franked.” My question: why “frank”? Who is Frank? It seems obvious there’s a connection between the two instances of the term, although I’ve learned that anything the government does that seems obvious probably isn’t. John Sieverts, Alexandria, Virginia

Cecil replies:

This one’s complicated. Steel yourself.

(1) The basic meaning of frank is free, as in frank discussion. This comes from the Franks, as in Charlemagne, King of. The Franks, being the dominant people in their neck of the woods, were the only ones with full freedom and their name became synonymous therewith. The Slavs, on the other hand, were the regional doormat and their name eventually evolved into “slave.” Nice.

(2) Frank or franked mail = free mail.

(3) Originally letters were signed individually in the place where the stamp was supposed to go, but when that got to be too much of a burden rubber stamps and later stamping machines were used.

(4) Cash register companies evidently have now decided that frank means “to stamp with a machine,” or more precisely, “to write upon with some electronic gadget that customizes the content of the message depending on the circumstances attendant thereto.” So I guess we can’t beef if they just say “frank.”

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.