From Middle English forthy, from Old English forþȳ, forþon (“because, since”), from for + þȳ, þon (“by that, therefore”), instrumental case of þæt (“that”); compare Old Norse fyrir því (at) (Danish & Norwegian fordi (“because”), Swedish för att). More at for, the.
forthy (not comparable)
- (obsolete) Therefore.
- "Forthy as now, I purpose for to wryte...Forthy as now schortlie to conclude"--Robert Henryson
- (obsolete) For this, for this reason; on this account.
- "Thomalin, have no care for thy."--Spenser.