Search:

Aha. Neuter nouns with the siffixes -к-, -чк- often (maybe, always — ?) have -и in plural: окошко → окошки, сердечко → сердечки.
I don’t know why.

That’s ruins of dual — grammatical number for pairs of things that used to exist in Old Rissian. In modern Russian, there’s no dual, but some words keep dual forms in plural.
Shoulders and ears are...