between: [OE] The second syllable of between is related to two and twin; the word as a whole seems to represent an original phrase meaning something like ‘by two each’. Old English betwēonum reflects a Germanic *twēon, reduced from an earlier *twikhnai; this represents the base *twīkh- (from which we get two) plus an -n suffix with apparently some sort of distributive function. The related betwixt comes ultimately from Germanic *twa ‘two’ and the element *-isk- ‘-ish’. => twin, two[between etymology, between origin, 英语词源]