c.1375 (n.), "act of going back," from L.
regressus "a return," from
regress-, pp. stem of
regredi "to go back," from
re- "back" +
gradi "to step, walk" (see
grade). The verb meaning "to move backward" is recorded from 1823; the psychological sense of "to return to an earlier stage of life" is attested from 1926.
Regressive is recorded from 1634; in ref. to taxation, it is attested from 1889.