Therefore
来自Big Physics
wiktionary
From Middle English therfore, therfor, tharfore, thorfore; synchronically a univerbation of there(pronomial adverb) + for. Compare Saterland Frisian deerfoar, Dutch daarvoor, German dafür, Danish and Norwegian derfor, Swedish därför.
etymonline
therefore (adv.)
Old English þærfore; from there + fore, Old English and Middle English collateral form of for. Since c. 1800, therefor has been used in sense of "for that, by reason of that;" and therefore in sense of "in consequence of that." Similar formation in Dutch daarvoor, German dafür, Danish derfor.
