As short as that expression is, there are at least two major errors in it. Short knicker!
The first is that the idea of knicker already indicates that whoever is putting it on is not wearing trousers. He is wearing something short. So, we do not need that word, ‘short’ again. Do we have long knickers? When you say ‘short knicker’, your expression thus exemplifies redundancy (using an expression that is not needed because it contributes nothing to the meaning of a phrase or clause). You can, as a matter of fact, use ‘shorts’ independently to refer to the dress. So, it is either ‘He wants to wear shorts’ or ‘He wants to wear knickers.’
The second error in ‘short knicker’ is that the full and correct term is ‘knickers’, not knicker. The reason is that the term falls among those referring to items that come in pairs, and are thus normally treated as plurals. As a result, they not only bear s, they also select plural verbs. Other examples are trousers, pants, braziers/bras, shorts, sandals, shoes, slippers and glasses. Even when you are referring to a pair being put on by someone, add the s, and let the plural verb follow it:
Where is my other short knicker? (Wrong)
Where are my other knickers? (Correct)
The knickers I’m wearing now is dirty. (Wrong)
The knickers I’m wearing now are dirty. (Correct)
You don’t want to wear the shoe. You mean it’s dirty? (Wrong)
You don’t want to wear your shoes? You mean they are dirty? (Correct)
I can’t read well because my glass is not here. (Wrong)
I can’t read very well because my glasses are not here.
I learnt the sandals he wants to wear is dirty. (Wrong)
I learnt the sandals he wants to wear are dirty. (Correct)
If you need a slipper to wear, I will give you.
If you need slippers to wear, I will give you. (Correct).
The following are also correct:
The pair of trousers he bought is from London.
A pair of sandals was seen beside the table.
The five pairs of trousers have been sold.
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