How did the "-ish" suffix come to denote the approximate meaning of the word it is attached to?
I only know the suffix is currently informalish. What is its provenience? What was the original meaning?
The suffix -ish comes from Old English -isc and is a diminutive.
So it means the word is lessened in intensity. Normalish (while not a proper word) means a bit normal. Yellowish means the thing is a bit yellow. Smallish means something is small, but not overly so.