For example, switching out the word 'boot' for 'trunk', or ditching the word 'rubbish' for 'garbage'.

This is something I've noticed my 6 year old does pretty regularly. We went through a stage where 'sweets' became 'candy', 'holiday' became 'vacation' and 'courgette' became 'zucchini'.

That last one didn't happen but if you're still reading you've got my respect, or as the Americans might say '...mad props'.