Hertz measures cycles per second - one Hertz is one cycle per second. Unlike gauss that is a measurement unit for the strenght of a specific thing (an electromagnetic field), hertz is a generic frequency measurement.
Prepend is a word that means to attach content as a prefix. It is often used in different kinds of programming and in automated processes. Some prepending is done manually as a user. For example, a prepend command could be used in a scripting language that a programmer would enter into a certain function or code module. It would add certain characters of text to the beginning of some variable or object.
Amend, emend both mean to improve by correcting or by freeing from error. Amend is the general term, used of any such correction in detail: to amend spelling, punctuation, grammar. Emend usually applies to the correction of a text in the process of editing or preparing for publication; it implies improvement in the sense of greater accuracy: He emended the text of the play by restoring the original reading.