Whole, universal, or rival
Emmaly is a modern phonetic variant of Emily or Emma. It likely draws its meaning from the Germanic 'ermen' meaning whole or universal, or the Latin 'aemulus' meaning rival.
Less common today
Emmaly isn't in the latest US Top 1000. It last peaked at #4,022 in 2007.
US births per 5-year period, 1990βpresent (SSA data).