odd: [14] The etymological idea underlying odd is of ‘pointing upwards’. Its ultimate ancestor is a prehistoric Indo-European *uzdho-, a compound formed from *uz- ‘up’ and *dho- ‘put, place’ (source of English do). From the notion of a ‘pointed vertical object’ developed ‘triangle’, which in turn introduced the idea of ‘three’ and ‘one left over from two’, hence ‘indivisible by two’. This is the meaning odd had when English borrowed it from Old Norse oddi, and the modern sense ‘peculiar’ (as if the ‘odd one out’) did not emerge until the late 16th century. => do
