What does Boxing Day have to do with boxing?
late 14c., from Old French registre (13c.) and directly from Medieval Latin registrum, alteration of Late Latin regesta "list, matters recorded," noun use of Latin regesta, neuter plural of regestus, past participle of regerere "to record; retort," literally "to carry back, bring back" from re- "back" (see re-) + gerere "carry, bear" (see gest).
Also borrowed in Dutch, German, Swedish, Danish. Some senses influenced by association with Latin regere "to rule." Meaning in printing, "exact alignment of presswork" is from 1680s. Musical sense is from 1811, "compass or range of a voice or instrument," hence "series of tones of the same quality" (produced by a voice or instrument). Sense "device by which data is automatically recorded" is 1830, from the verb; hence Cash register (1875).
late 14c. (transitive), "enter in a listing," from Old French registrer "note down, include" (13c.) and directly from Medieval Latin registrare, from registrum (see register (n.)). Intransitive sense, of instruments, from 1797; of persons and feelings, "make an impression," from 1901. Meaning "to enter one's name in a list" for some purpose is from 1940. Related: Registered; registering. Registered nurse attested from 1879.
To express with the face and body: I jumped up and registered horror (1901+)