repetitious adj.

late 14c., repēten "to say what one has already said," from Old French repeter "say or do again, get back, demand the return of" (13c., Modern French répéeter) and directly from Latin repetere "do or say again; attack again," from re- "again" (see re-) + petere "to go to; attack; strive after; ask for, beseech" (from PIE root *pet- "to rush, to fly").

Meaning "say what another has said" is from 1590s. As an emphatic word in radio broadcasts, 1938. Meaning "do over again; do, make, or perform again" is from 1550s; the specific meaning "to take a course of education over again" is recorded from 1945, American English. Intransitive sense of "perform some distinctive (but unspecified) function again or a second time" is by 1714. Related: Repeated; repeating.

word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (compare -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."

"containing repetitions, characterized by or of the nature of repetition," 1805, from Latin repetit-, past-participle stem of repetere "do or say again" (see repeat (v.)) + -ive. Related: Repetitively; repetitiveness. Other adjectives, in addition to repetitious (1670s) included repetitionary (1720), repetitional (1720).

repetitional, repetitionary, repetitious, repetitive. With all these on record, repetition would seem to have a good stock of adjectives at need ; but few writers have the hardihood to use any of them. Repetitious is said to be 'common in recent American use' ; repetitive is perhaps the least avoided in England. [Fowler, 1926]