Is it normal for a child to substitute something completely random in place of a word they can't remember?
I said to DD2, "You've got a big curl in your hair." when she'd got out of bed. She asked to feel it, then said "Is it 'cuplax'? then shook her head and said 'cutlox....you know that thing where DD3 gets really big hair."
She was thinking of bed-head.
I, of course, don't know what's normal for a 5 year old.