From everything I can find,
Eino seems to be a strictly male name. The feminine form is
Eini. The parents naming their daughters
Eino might be looking at it as a unisex name. Are you sure their names weren't
Eini? The name was popularized by a poet named
Eino Leino, and his full name was
Armas Einar Leopold Lönnbohm. I'm not certain, but it looks like "
Eino" came from the name
Einar in his case. It seems like
Eini and
Enni are the official feminine forms of
Eino.