also back-pack, 1904, "bag with shoulder straps that allow it to be carried on a person's back," from back (n.) + pack (n.). By 1916 as a verb, "to hike while carrying supplies in a backpack." Related: Backpacked; backpacking.

also back-space, 1899, in reference to keyboarding, from back (adv.) + space.

We have had the pleasure of examining one of the 1899 model Hammond typewriters, with the new back-space key. This new feature is certainly an improvement in the machine. [The Phonetic Journal, March 11, 1899]

also back-stage, "the area of a theater out of view of the audience," especially in the wings or dressing rooms, 1891; see back (adj.) + stage (n.).