This question on Latin.SE asks about the "elliptical dual", a construction where the dual number doesn't mean "two X" but instead "X and one other". For example, in the Iliad, Aíant-e
Ajax-DUAL means not "the two Ajaxes" but "Ajax and Teucer".
Similarly (from the answers and comments on that question):
- Sanskrit ahanī
day-DUAL"day and night"
- Latin Castor-ēs
Castor-PLURAL"Castor and Pollux"
- Arabic al-qamarāni
the-moon-DUAL"the sun and moon"
From my rudimentary knowledge, Japanese also seems to have a similar construction: Yuki-chan-tachi
Yuki-DIM-PLURAL "Little Yuki and her friends".
I'm curious how widespread this phenomenon is. In English we don't seem to use the plural like this, but are we the outliers? Some of the examples here seem to come from Proto-Indo-European, but Arabic and Japanese certainly don't.