In WW1 the Brits called the things "tanks" because that was the code word for them. The name stuck, much more so than the official name "armor" or "armored vehicle".
I guess Turtledove decided "tank" is too much of a British word, and since in his TL the Yankees invented the first tanks (on the north american continent) they get a proper American code name.
I guess Turtledove decided "tank" is too much of a British word, and since in his TL the Yankees invented the first tanks (on the north american continent) they get a proper American code name.