Why is 'lovely' not accepted? I use it interchangeably with 'pretty' or 'beautiful'.
I think it is because the hat is probably ment for men not for women, and pretty is a word not often used to compliment men?
In Biblical Hebrew the word כּוֹבַ֫ע was stressed on its last syllable and only the construct form כּ֫וֹבַע־ retracted the stress onto the penultimate like in כּ֫וֹבַע־נְחָ֫שֶׁת (1Sam 17.5) helmet of brass. It seems as if the stress on the penultimate has been generalised in Modern Hebrew, so that one always says ['kova].