Or is it grate?

Is it possible to mix the two up?  I don’t think so.

Great usually means: everything is great, or good, or excellent, whatever degree of goodness you want to put to it.

It could also mean something else, like:  Well, you were a great help! when in fact you want to say how useless they were.

Large or little.

Like all creatures great and small,  Why not say big or small.  Big doesn’t quite have the same effect.

Of course, you could be a great person, well, what I really mean is distinguished.  Besides, great could mean way above average, too.  Or grand, or impressive, the list goes on.

And haven’t we all, at some time had a great-aunt.  No not the good one, the ‘great’ one, denoting her seniority, not necessarily how nice she is.

As for the other grate, we can build a fire in it.

Or add an ‘un’ in front and ‘ful’ at the end, to denote what parents sometimes think of their children

Or get a block of cheese and ‘grate’ it into small shreds.

Or speak in a voice that grates on your nerves, possibly by that great-aunt.