Confuse
Middle English (in the sense ‘rout, bring to ruin’): from Old French confus, from Latin confusus, past participle of confundere ‘mingle together’ (see confound). Originally all senses of the verb were passive, and therefore appeared only as the past participle confused ; the active voice occurred rarely until the 19th century when it began to replace confound .
wiktionary
Back formation from Middle English confused ("frustrated, ruined"), from Anglo-Norman confus, from Latin confusus, past participle of confundō.
etymonline
confuse (v.)
1550s in a literal sense "mix or mingle things or ideas so as to render the elements indistinguishable;" from mid-18c. in the active, figurative sense of "perplex the mind or ideas of, discomfit in mind or feeling," but not in general use until after c. 1800. From 1862 as "erroneously regard as identical." It took over these senses from its older doublet, confound (q.v.).
The past participle confused (q.v.) is attested much earlier, in Middle English (serving as an alternative past tense to confound), evidently an adaptation of Old French confus or Latin confusus, "with the native ppl. ending -ED and the present stem a much later inference from it" [OED]. Related: Confusing.
