quick: [OE] Originally quick meant ‘alive’ (as in the now fossilized phrase the quick and the dead); it was not until the 13th century that the sense ‘rapid’ began to emerge. It goes back to a prehistoric Germanic *kwikwaz (which also produced Swedish kvick ‘rapid’); and this was descended from an Indo-European base *gwej-, which branched out into Latin vīvus ‘alive’ (source of English vivid), Greek bíos ‘life’ (source of English biology), Welsh byw ‘alive’, Russian zhivoj ‘alive’, etc.
The couch of couch grass [16] is a variant of the now seldom encountered quitch, whose Old English ancestor cwice may be related to quick (the allusion presumably being to its vigorous growth). => biology, vivid[quick etymology, quick origin, 英语词源]