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.
For the Assemblage 23 album, see Addendum (album). An addendum, in general, is an addition required to be made to a document by its author subsequent to its printing or publication. It comes from the Latin verbal phrase addendum est, being the gerundive form of the verb addo, addere, addidi, additum, to give to, add to, meaning (that which) must be added. Addenda is from the plural form addenda sunt, (those things) which must be added. (See also memorandum, agenda, corrigenda.)