ETYM Old Eng. Same as beside, prep.; the ending -s is an adverbial one, prop. a genitive sign.
1. In addition; SYN. too, also, likewise, as well.
2. Making an additional point; anyway; SYN. in any case.
Beyond what has been said; further; besides; in addition; furthermore; also; likewise.
De plus, davantage. Je lui ai donné tant, et en outre je l'ai nourri.