- It is related to второй ("secundus”) < OCS въторъ (“other”, "second”) < PIE *wi-tero- (“more apart”) < PIE base *wi- (“separation”) + comparative suffix *-tero- (“-er”).
How, if второй is from PIE *wi-? What derivational process would produce 'друг(ой)' from it? —Mucius Tever 02:25, 31 Octobris 2009 (UTC)
друг(ой)II from друг I. второй is a synonym.--Rogius 03:46, 31 Octobris 2009 (UTC) PS. Analogically, Alter ego (=amicus). All are epitheton, not noun. Definition not strict.
- I sort of guessed that II would be from I, but, if that's the case, then друг and второй are not related at all! —Mucius Tever 12:43, 31 Octobris 2009 (UTC)