Moreover means and on top of that. Moreover, the cost is rising, and moreover, it is late.
It adds a point that strengthens the one before, and it is formal, so it belongs to reports and arguments rather than to speech. It goes at the start of a sentence with a comma after it, and furthermore does the same job.
1adverbmoreoverAnd on top of that.
“The flat is too small; moreover, the rent is far too high.”
moreover is a connective.
Middle English more over, meaning further or beyond, written as one word by the fifteenth century.
Middle English
moreover
English, today
moreover
Middle English moreover, moreovere, morover, mooreover, more-overe, mare over, equivalent to more + over.
Etymology from Wiktionary, CC BY-SA