Tautologies are those things which say the same thing twice. The most famous is "round circles". As for me, I have never seen any square ones, so it is a tautology to talk about round circles. Another popular one is "egg omelettes" because it is hard to imagine any other kind. Of course, we may want to explain that it is not a Spanish omelette or a cheese omelette or similar. In this case, we might well be advised to say it is a plain omelette.
However, the same is not true of "potato flavoured crisps". In New Zealand, these are often called chips or chippies, Americans call them chips, Englishmen call them crisps and mistype them as crips. However, my uncle persisted in talking about "potato crisps" which was considered a tautology in England. In New Zealand, it is not! In New Zealand and elsewhere in the Pacific, you can find kumara chips, taro chips and a variety of other products cut into the same shapes.
If you have a chance to eat kumara chips, you should do so. However, the best kumara chips are hot one, like French fries but based on kumara rather than potato.
Excuse me, I seem to have wandered away from grammar and onto food. Where was I? Oh yes, tautologies - saying the same thing twice. A voice mail message I know and love begins with "I'm currently out of the office at the moment". Perhaps I could say it starts with that at the beginning, and then I would be guilty too. Tautologies are generally bad things, but they might have artistic merit. In "Song and Dance Man", Michael Gray analyses one of Bob Dylan's lines very carefully: "The finishing end is at hand." This he says, declare complete finality and a contrast to what might be seen as the end of something but which is, in fact, not the end at all.
If you would like to suggest some of your favourite tautologies, please mail me and I will include your example in an update of this page.