insteadyoudaoicibaDictYouDict[instead 词源字典]
instead: [13] Instead is the English end of a chain of loan translations that goes back to Latin in locō (in loan translations, the individual components of a foreign word or expression are translated into their equivalents in the borrowing language, and then reassembled). The Latin phrase meant literally ‘in place (of)’, and this was translated into Old French as en lieu de.

Middle English rendered the French expression in turn as in stead of or in the stead of (stead ‘place’, now obsolete except in certain fixed compounds and expressions, comes ultimately from the same Indo-European source as stand, station, etc). It began to be written as one word towards the end of the 16th century.
=> stand, station, statue, stead[instead etymology, instead origin, 英语词源]
instead (adv.)youdaoicibaDictYouDict
1590s, from Middle English ine stede (early 13c.; see stead); loan-translation of Latin in loco (French en lieu de). Still often two words until c. 1640.