Origin: Germanic Old English prefix
Besides has 4 different meanings across 2 categories:
making an additional point; anyway
"I don't want to go to a restaurant; besides, we can't afford it"
"she couldn't shelter behind him all the time and in any case he wasn't always with her"
Also; in addition.
"Besides the heavy rain, we also have to deal with a power outage today."
In plain English: Besides means in addition to something else.
"Besides being tired, I am also very hungry."
Usage: Use besides to mean also or in addition when introducing another point that supports your main argument. It functions naturally at the beginning of a sentence or clause to add information without implying exclusion.
In addition, in addition to.
"Besides the three tasks I already listed for you, please remember to submit your report by Friday as well."
The word besides comes from the Middle English phrase bisides, which was formed by adding an adverbial suffix to beside. It originally meant "in addition to" or "apart from," a meaning that remains its primary definition today.