The thumbs up sign is most commonly thought to descend from gladiatorial contests in which the audience determined whether the combatant was eligible to live or die by a thumbs up/ thumbs down vote. But at this time the thumbs up sign indicates divers meanings like when people ask to someone whether a job is going well or not, showing his/her thumbs up is present positive reaction. Also when people praise someone, and the sign includes meaning of 'you are the best' as well. As a result the meaning of thumps up sign has been expanded as a sign stand for affirmative reaction which is being used world-wide.
Salute
The military salute is traditionally performed by touching the eyebrow with four fingers together. Roman soldiers are thought to have initiated the procedure as a sign of shielding their eyes from the great light of their superior officers. Knights may have used it to raise their helmets as an indication that they did not intend to fight. This theory is supported by the fact that the helmet on a suit of armor is called a “sallet,” very close to the word “salute.”
In my opinion, performing the military salute makes soldiers feel a sense of belonging in one group and also work as an identifier. Therefore it strengthens the unity of troops so it is may assumed that uses of performing salute was changed and used intentionally dislike other symbols.
Peace Symbol
The peace symbol is one of the most widely known symbol in the world, in Britain it was designed as standing for nuclear disarmament and in particular as the logo of the Campaign for Nuclear Disarmament (CND) but In the United States and much of the rest of the world it is known more broadly as the peace symbol.
Pigeon
Pigeon is an animal that widely known as a symbol of peace but its meaning has been changed recently. By increasing the number of pigeon in urban area, their droppings are cause of few problems. Their high acid droppings damage buildings and vehicles also pollute the public area. In addition it contains a virus that provoking cause of meningitis to human. For these reasons above many cities struggle to reduce their number and announced a pigeon as a harmful animal to human and allow people to kill pigeon.
Mobile Phone
In the early 90's when the mobile phone first came out it was a prestige address because of its enormous expense of maintenance and also the fact that it represented high-technology of the age. Then time went by, development of technology helped to reduce its production cost and became more common.
It lost its symbolic meaning of the time it emerged but new meaning has been imparted to the mobile phone by Improvement of IT technology, sales strategy of multinational corporation companies and popularisation of the internet. At this present a smart phone carries out a variety functions and being presented as an icon of information age.
This process has been occurred within about 10years, now a mobile phone is a symbol of communication. I personally think that as a designer we always should be prepared in ear of rapid technological change.