Apparently it's also related to the Italian grasso, the Spanish graso and the French gras (as in Mardi Gras. Give a cheer to Superjey.) All of which look back at the old Latin crassus (which means "thick, fat, overweight) (remember that next time you find some Roman guy named Crassius in a story or movie.)
Where it comes from before that? I have no clue.
As for a relation to grease? Quite possibly. but it's late and I need to get up in the morning.
According to etymonline.com: Yes. English "grease" derives from the same source as grasso/graso/gras.
Does this word for fat mean "to be fat" aswell? Could you say "ŝi estas grason"? As in overweight.
For that you could use the adjective "korpulenta". "Li estas korpulenta".
"Grasa" is also an option, but it also means fatty, greasy.
You could also say dika, which is more common than korpulenta in everyday usage (though both are correct).
Nouns end in -o. Adjectives end in -a.
Also, the copula (stative verb) "to be/esti" does not take direct objects, so it would not be marked with -n.
"*manĝi grason por vivi"
Ho ve, oni devas manĝi almenaŭ iomete da graso, estas bezonata por daŭre vivi laŭ biologiistoj :P
Does this mean that she doesn't eat a piece of grease? Because if it's about how she eats then it should be grase right?
Discrete piece vs mass quantity aside, you can tell that fat is the thing she doesn't eat because it's marked as a noun (-o) and as a direct object (-n).
Yes, adverbs end with -e, although not everything makes sense as an adverb. I can parse "She eats greasily", (and apparently "greasily" is a recognized word) but it's not really a usual thing to say.
Lard in Esperanto is porkograso
Lardo in English is bacon
I hope that this is clear.
No, because "lard" is specifically pig fat. The translation calls for fat in general.
I hate to go to the internet to copy Esperanto letters that doesen't exist on my keyboard
Duolingo has buttons to type those letters. You can also use an AutoHotkey script if you want to create keyboard shortcuts for them