This is so cool. After having to tell my stepson that I have no idea why “to go” is such a bizarre irregular verb in English, I now have an answer. Turns out that go was a synonym of wend, up until the 15th century, when go won out and wend fell by the wayside. But the past tense of wend was went — which continued to be used. And the past tense of go was goed, which was dropped. Thus the present tense go was paired up with the past tense went, and now we have one modern verb that’s mashed together from two old ones. No wonder it’s so weird!
I picked this up from a Mental Floss post on dead words that persist to this day only because they were “fossilized in idioms,” a phrase I loved the moment I read it. Check out the link for 11 others. My favorite, after wend, is roughshod. I never knew what that actually meant. Now that I do…ouch.