Otherwise

google

ref

Old English on ōthre wisan (see other, wise2).

wiktionary

ref

From Middle English otherwise, othre wise, from Old English on ōþre wīsan(literally “in (on) other/different manner”); equivalent to other +‎ -wise. Compare West Frisian yn oarwei(“otherwise”), Icelandic öðruvísi(“otherwise; else”).

etymonline

ref

otherwise (adv.)

contracted from Old English phrase on oðre wisan "in the other manner" (see other + wise (n.)), which in Middle English became oþre wise, and mid-14c. oþerwise. As an adjective from c. 1400. Also in Middle English were otherwhere "elsewhere;" otherwhat "something else" (pron.).