Filler text (also placeholder text or dummy text) is text that shares some characteristics of a real written text, but is random or otherwise generated. It may be used to display a sample of fonts, generate text for testing, or to spoof an e-mail spam filter. The process of using filler text is sometimes called greeking, although the text itself may be nonsense, or largely Latin, as in Lorem ipsum.
Asdf
ASDF is the sequence of letters that appear on the first four keys on the home row of a QWERTY or QWERTZ keyboard. They are often used as a sample or test case or as random, meaningless nonsense. It is also a common learning tool for keyboard classes, since all four keys are located on the home row.
Etaoin shrdlu
Main article: Etaoin shrdlu
“Etaoin shrdlu” is the approximate order of frequency of the twelve most commonly used letters in the English language, best known as a nonsense phrase that sometimes appeared in print in the days of “hot type” publishing due to a custom of Linotype machine operators.