Such a foot is called an iambus (plural, iambuses, or the Latin iambi), and the form of verse is called iambic.
It was not by chance that the line of five iambuses became the dominant metre of our language.
The seventh and last form of our Iambic measure is made up of seven Iambuses.
There are in both three series of iambuses—the dimeter, the cataleptic trimeter, and the acataleptic.
It does not have to consist of five iambuses only, but other feet may be substituted almost at the caprice of the poet.