Why does went bear no relation to its main verb,to go? Why don't we say goed?
Went once belonged to another verb, the verb 'to wend', now rather archaic in English, but still occasionally heard in the phrase 'wend one's way', as in the first sentence of this recent newspaper article: "Walkers in South Yorkshire are being invited to wend their way around Wentworth ...", or in the second paragraph of this Daily Telegraph piece about global banking reform: "A large pile of legislation has already started to wend its way through the European Parliament ...", or in the first sentence from this football match report in a Scottish newspaper: "As the game approached its conclusion and the crowd wended its way into Sinclair Street".
By around 1500 went had become associated with the verb 'to go', whilst the verb wend had gained the regular past tense wended. The original meaning of to wend was 'to turn' (note that in German wenden still means 'to turn'). Later it came to mean 'to move' generally and then 'to go in a particular direction'.
This process - where a verb form has come from a completely different root - is called suppletion. Note that the past tense of undergo and forgo, which are formed from the verb go plus a prefix follow the same pattern as go - underwent and forwent. However, it's embargoed, not embarwent, because embargo is not made up of embar + go; it is from the Spanish word for 'to impede'. Similarly, it's tangoed and pogoed.